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EARL WARREN. Co>'«"'or 


Fffrry Building, Son FranciKO 

OlAF P. JENKINS. Clii«f 

Son Francisco 

Bulletin 158 

December 1952 




Associate Professor, Oeporrment of Geological Sciences 
University of California, Berkeley, California 




To His Excfxlenxy 
The Honorable Earl Warren 
Governor of the State of California 

Dear Sir: I have the honor to transmit herewith Bulletin 158, Evolution of 
the California Landscape, prepared under the direction of Olaf P. Jenkins, Chief 
of the Division of Mines, Department of Natural Resources. This volume is pro- 
fusely illustrated with photoo;raphs, maps, and drawings, characterizing the sig- 
nificant surface features of the entire State. The author. Professor Xorman E. A. 
Hinds of the Department of Geological Sciences, University of California, has 
systematically described those surface features as they are related to the geology 
and rock structures of the State, and has shown how these features have developed 
through natural processes operating over the long periods of time required to pro- 
duce California's diversified landscape. 

HuUetin 158 should find a useful place in the schools of the State and among 
those persons who love to travel and admire California. It should help to increase 
enjoyment of what is to be seen by explaining thoroughly why the surface features 
are what thev are. 

Respectfully submitted, 

Warren T. Hannum, Director 
Department of Xatural Resources 

Approved : 
W. T. H. 
November 17, 



FRONTISPIECE. Sierra Nevada west of Bridgeport, Modo County. Photo by C. W. Chcsterman. 



Introduction 7 

Sierra Nevada n~- 

Basin-Kanges 61 

Mojave Desert 87 

Colorado Desert 97 

Modoc Plateau 109 

Cascade Range 117"~ 

Klamath Mountains 137 — 

Great Valley 143— 

Coast Ranges 155, 231 — 

Transverse Ranges 183 

Peninsular Ranges 195 

Sea Floor 217 

Index 233 

( 5 ) 



California may be divided into a number of units called geomorphic 
provincfs (the Sierra Ne\-ada. Basin Ranges, Mojave Desert, Colorado 
Desert, Modoc Plateau, Cascade Kanjre, Klamath Mountains, Great 
Valley, Coast Ran<res. and Transverse Ran^res geomorphic provinces 
shown on plate 2), each of which is characterized by a distinguishing 
{reological record, particularly in tlie later part of earth history, and 
by more or less uniform relief features or combinations of features 
throughout its area. These geomorphic provinces are remarkably 
diverse, and in the midst of some of them great numbers of people 
live ; others, more distant, are visited by an increasing host each year. 
Frequent requests are made for the geologic story of Yosemite Valley, 
Lake Tahoe, Death Valley. Mount Sha.sta. the great ranges extending 
eastward from Los Angeles and the bold shore features of California. 
As with music, literature, the arts, or anything else, the more one 
understands about what he is hearing, reading, or seeing, the more 
interesting it becomes. So far no book has been written which tells the 
story of the evolution of California's landscape. There are technical 
papers and reports about many areas, but they are in the language 
of the scientist, much of which is like a foreign tongue to the laT.Tnan, 
and they contain a great amount of information of interest only to the 
specialist on the subject. Therefore, in this volume an attempt is made 
to bring together information about the various parts of the state in 
a fashion which those uninitiated in the complex vocabulary of 
geologj- can understand. The book is not intended for the trained 
geologist, but for the layman who wants to learn more about places 
he has seen or may see. Included are abundant pictures, sketches, and 
diagrams, for these often make clear what written words can not. 
Furthermore, the illustrations may awaken many people to the mjTiad 
of scenic wonders lying within California's boundaries, wherein is 
perhaps the most remarkable collection of natural masterpieces to be 
found in any state of the Union. 

Because of California's huge area, studies of many parts are incom- 
plete or not even made, so w-e have only a partial picture of how the 
landscape reached its present form ; none the less, enough information 
is available so that all of the major divisions can be described in, 
general outline at least. The state is so large and its geological history 
is so complex that no single person can know by any means all of it, 
for field study is slow. Therefore it has been neeessarj' to draw freely 
on the writings of others. In order to avoid referring to so many 
writers in the text, practically all names have been omitted, but the 
significant publications have been listed at the end of each chapter. 
By these lists acknowledgment is made of use of information which 

many workers have gathered ; they serve as sources for further read- 
ing for any who are particularly interested in a certain section. 

The following books give fundamental presentations of landscape 
evolution ; the first three are intended for elementary college courses 
in the subject and for the lay reader; the last three are somewhat 
more advanced. 

Hinds, N. E. A., Geomorphology, Prentice-Hall, Inc., New York, 1&43. 
Lobeck, A. K., Geomorphology, McGraw-Hill Book Company, New York, 1939. 
Worcester, P. G., A textbook of geomorphology, 2d ed., D. Van Xostrand 

Company, 1948. 
Cotton, C. A., Landscape, 2d cd., Whitcombe and Tombs, Ltd., Wellington, 

X. Z., 1948. 
Cotton, C. A., Geomorphology, 5th ed., John Wiley and Sons, 1949. 
Von Engeln, O. D., Geomorphology, The MacMUlan Company, 1942. 

Geomorphology is the technical name for the scientific study of land 
forms and landscapes, being derived from three Greek words ge- 
earth; morphos- form; logos, science or study. In former j-ears, this 
subject was termed physiography and a number of books, now largely 
out of date and mostly out of print, were written under this title. 

The reference volumes listed above are well illustrated, so that they 
give the reader an excellent pictorial view of the earth's land forms, 
as well as descriptions of their origin. 

For those who are particularly interested in rocks and minerals, 
the following books of rather popular nature are suggested : 

English, G. L., Getting acquainted with minerals, Mineralogical Publishing 

Co., Rochester, N. Y., 1934. 
Fenton, C. L., and Fenton, M. A., The rock book, Doubleday and Company, 

Inc., New York, 1946. 
Hurlbut, C. S., and Dana, E. S., Minerals and how to study them, John Wiley 

and Sons, Inc., 1949. 
Murdoch, J., and Webb, R. W., Minerals of California, California Division 
of Mines Bull. 136, 1948. 

The Earth's Age 

Although the age of the earth has been a much-debated topic for 
centuries, recent improvements in scientific tools have allowed a more 
accurate estimate to be made now than ever before. With the advent 
of our knowledge of radioactivity, a new means for determining the 
age of some earth materials was evolved, and the findings enormously 
expanded the known length of earth history. Radium is an element 
developed by the natural breakup of atoms of parent elements like 
uranium, thorium, and actinium, which are contained in a few min- 
erals of the earth. During the disintegration of the atoms, the valuable 
gas helium also is generated. Radium itself decomposes into other 
elements, so that we have a radioactive series. The final product of 
this natural change seems to be one of the isotopes of lead. Isotopes 
are varieties of elements having the same atomic numbers, virtuaUy 




[Bull. 158 

the same cliemioal properties, but differing slifrhtly in atomic weights. 
The lead-isotope formed from decay of parent radioactive elements 
apparently does not break up, and the rate of decomposition has been 
accurately measured in terms of the half period of decay. Therefore if 
an uranium- or thorium-bearing mineral is present in a rook, the ratio 
of the uranium and thorium content and the helium and lead isotope 
content can be determined. Only minerals from fresh or relatively 
fresh volcanic rocks can be used, for in these alone the significant 
mineral grains have been altered or disturbed to the least extent and 
material of mixed source is not present. Certain corrections have to 
be made to allow for changes which have occurred since the mineral 
was formed so that the calculations are complicated. Helium seems 
less satisfactory for the determinations than lead, probably because 
it can escape more easily from rocks than the solid element. The oldest 
known minerals come from Russia and Manitoba, Canada; their ages 
are 1,850 and 2.300 million years respectively. Because volcanic rocks 
have been erupted at various places over the earth or emplaced below 
its surface during the entire known history, an approximate time 
scale has been set up. This undoubtedly will be made more accurate and 
fuller as techniques are improved and more determinations of mineral 
age are made. 

There are serious discrepancies between determinations based on 
helium and those based on radio-lead, but, in spite of this, all measure- 
ments so far made indicate that the recorded history of the earth 
probably exceeds a billion and a half years. Back of this known record 
there is a long interval, perhaps a half billion or more years, from the 
earth's origin to the formation of the oldest known rocks. The age of 
the earth thus is between two and three billion years. 

To facilitate discussion of events which have taken place over this 
immense span of time, it has been divided into ma.jor units called 
eras: these are composed of briefer intervals termed periods, which 
in turn are separable into still .shorter time units known as epochs. 
The passage from one geological era to another has been marked by 
many profound changes. Over long intervals, but short as compared 
with the length of the era, the continents have grown very large, and 
mountain ranges have been built in various parts of the earth. Cir- 
culation of the ocean and the atmosphere has been conspicuously 
altered by these geographic changes, with consequent important cli- 
matic modifications. The changes between periods and epochs are 
less pronounced. For example, an era, called the Mesozoic, ended 
about GO million years ago as the result of such events as are described 
above, and a new one, the Cenozoic was initiated. We live in the latter 
era, which is composed of one period, the Tertiary, and this period 
is divided into five epochs, the Eocene and Oligocene, or early Ter- 
tiary, including 40 to 4.3 million years, and the Miocene, Pliocene, and 
Pleistocene, or late Tertiary, covering 15 to 17 million years. The 

Di.TEriim showing three stages in the evolution of a geosyncline. Top: 
Highlnnd and .idjoininc lowland. Sediment transported from the erosion 
area is deposited on tlie lowland. Center: Lowland invaded by shallow 
ocean. Floor of the basin subside.s under load of debris. Bottom: Trough- 
iiiie depression called geosyncline is formed by continued deposition. Strata 
mav be tens of thousands of feet thick in center of geosvncline. See p. 15. 
.V. E. A. Hindi. GEOMOKPIIOLOGY (copyright 19^3. hy Prentice-Hall 
Inc., A^etc York}. Reproduced hy permission of the publisher. 

Pleistocene epoch commenced one or two million years ago, and is one 
of the most remarkable interludes of earth history. 

The following discussion of the landscape of California is con- 
cerned principally with events which took place during the Cenozoic 
era ; but some dating as far back as the Jurassic and Cretaceous 
periods of the Mesozoic era also are of great significance. Mesozoic 
time is divided into three periods, the Triassic (which represents 
about 30 million years), the Jurassic (40 million years), and the 
Cretaceous (55 million years) closing the era. Each of these periods 
left an imposing record in various parts of the state. In landscape 
evolution, the first imprints recognizable in California today were 
made in Jura.ssic time, when the ancestors of the Klamath Moun- 
tains, the Sierra Nevada, part of the Transverse Ranges, the Penin- 
sular Ranges, and some other ranges appeared. 




Fio. 1. Sierra Nevada, showing Junction Peak and Diamond Mesa. Photo by Oeorge J. Young. 


Hugrest of the mountain ranges in California and one of the most 
massive in North America is the Sierra Nevada, which lies along a 
considerable stretch of the eastern boundary of the state. In lenpth 
the range measures about 430 miles, in width from 40 to 80 miles; 
a goodly number of its peaks exceed an elevation of 12.000 feet above 
sea level, and Mount Whitney (14.496 feetl is the highest spot in the 
United States. Dr. F. E. Matthes of the United States Geological 
Survey, who for many years .studied Sierran geology, states that "the 
range stands higher above its immediate base than any other" in the 
country. "The Rocky Mountains, many of whose summits rise above 
14.000 feet, stand only 9.000 feet above the Great Plains to the east 
which attain altitudes of about 5.000 feet at the foot hills; but the 
Sierra Nevada stands not less than 11,000 feet above Owens Valley 
at its eastern base and 14,000 feet above the Great Valley of California 
at its west base. ' ' 




KiG. 2. Cross section of the Rierrn Nevada. California, through Xlt. Whitney, 
its hichei«t peak. The boundar.v fault s.vstem along which the range has been elevated 
l>.v tilting is shown on the right-hand side of the section. In this part of the range, 
most of the rock exposed at the surface is granite, but there are considerable areas 
of the intensely folded and faulted bedrock into which the granite was intruded. 
Alter F. E. Slatthe; U. S. Oeol. Survey Prof. Paper ISO, p. 25. 

Most of the range trends slightly west of north, but at the southern 
end the direction changes to west of south. Strikingly contrasted are 
the two slopes : that to the west of the crest is broad and gentle, but 
that to the east is much more steeply inclined. Because of this unsj-m- 
metrical cross section, the crests of high peaks lie only a few miles 
from the eastern boundary of the Sierra Nevada, but from 30 to 70 
miles from the western base. At the northern end of the Sierra, peaks 
of highest elevation are between 6.000 and 7,000 feet ; near Lake 
Tahoe, Pyramid Peak, Mount Tallac, and other mountains in the 
vicinity are 9.000 to more than 10,000 feet high ; in Yosemite National 
Park, the peaks reach 12,000 to 13,000 feet in elevation ; and in Mount 
Whitney region the highest peaks are found — Mounts Williamson 
(14,384 feet) and Langley (14,042 feet), and, of course. Mount 
Whitney itself (14,496 feet). Farther south elevations decrease to 
about 6,500 feet where the Sierra Nevada province adjoins the Cali- 
fornia Coast Ranges near Tehachapi Pass, nearly 100 miles from 
Mount Whitney. 

Because of the gentle ascent from the Great Valley, the western 
side of the Sierra Nevada does not present a particularly imposing 
spectacle, though the crest peak.s, in the highest part of the range, 
stand out in striking fashion. Part of the ea.stern side, on the other 
hand, is one of the most imposing mountain escarpments in the world. 
The northern section is not impressive, for it is lower and is split 
into minor ranges branching off in a northerlj- direction from the 
main range. From near Lake Tahoe southward the front is higher 
and less broken. It rises about 6.000 feet above Mono Lake, 10,000 
feet at the head of Owens Valley west of Bishop, and more than 11,(K)0 
feet near Mount Whitney. Then as the range decreases in height 
farther south, the escarpment lowers. In the Owens Valley section in 
particular, the eastern face appears to be an almost vertical declivity 
towering above a rather even lowland. This illusion is dispelled, how- 
ever, by actual measurement of the slope of the front which in feV 
places exceeds 25 degrees. The highest section is immediately west of 
Lone Pine. From there Mount Whitney is visible, but elsewhere in 
Owens Valley this peak cannot be seen since it is located at the head 
of a great canyon far back from the main front. The most conspicuous 
peak seen from Owens Valley is Mount Williamson, which stands out 
because of its particularly ragged form and its position more than a 
mile to the east of the main divide. Mount Langley is a somewhat lower 
peak but also presents an imposing appearance ; Lone Pine Peak 
(12,951 feet), which stands about 2 miles east of the main crest, 
rises directly above Owens Valley, and appears to be even higher than 
Mount Whitney. 


Since the Sierra Nevada parallels the Pacific coast, it forms a 
gigantic barrier lying athwart the path of the prevailing westerly 
winds, which most of the time carry moist air from the Pacific Ocean 
over the continent. The Coast Ranges farther west are too low to rob 
the air currents of much of their moisture except at their northern 
end where rainfall is heavy. As the winds ascend Sierran slopes to 
elevations where temperatures are lower, condensation gives abundant 
winter and spring snow and rain. Most of the precipitation falls on 
.the western side increasing rapidly from about 4,000 feet and decreas- 
ing above 6,500 feet, according to the U. S. Weather Bureau, though 
Dr. Matthes puts the limit of heavy snow and rain at 9,000 feet. Below 
4,000 feet the climate is .semi-arid but less dry than in the Great 
Valley to the west. Above 9,000 feet it also is relatively dry because 
of the heavy extraction of moisture below that level ; however, snow 
hangs much later in the year on the higher peaks because the longer 
duration of cold weather retards melting, the snow disappearing in 
June, July, or even August, and returning commonly in October. 




[Bull. 158 

KiG, 8. Ensl face of the Sierra Nevada as seen frcnn (")\vens \'alley. Tbe boundary fault system lies immediately at the base of the ranee. In the foreground is part of the 
Owens Valley Kraben. Krosion has modelled the scarp into a series of det-p canyons, most of which are glaciated in their upper parts, separated by steep-sided narrow-crested 
ridces. J'halu by U'. C. Mendenhall. courtesy U. »S'. Geological Survey. 

Within the zone of heavy precipitation, depth of winter snow 
exceeds that in any other part of the United States except the Olympic 
Mountains in northwestern Washin<;ton, the northern part of the 
Cascade Ranpe farther east in the same state, and perhaps certain 
sections of the Rocky Mountains. Between elevations of 6,000 and 7,000 
feet alonj; the Southern Pacific Railroad, the annual snowfall amounts 
to 30 or 40 feet with as much as 60 feet fallinj; in some years; at 
Norden Station (elevation 6.871 feet) the averajje yearly fall over a 
34-year period is 34 feet. At Tamarack in Alpine County (elevation 
8,000 feet), 73.5 feet of snow fell in 1906, the greatest amount ever 
recorded for the entire Sierra Nevada. Frequently there are 10 to 12 
feet of snow on the "rround at a single time and in protected spots the 
pile may reach 30 to 40 feet deep. Again at Tamarack during the 
winter of 1906-07, 8.8 feet of snow fell during a single storm, another 
record for the whole of the range. 

Because the winds lose so much of their moisture as they travel up 
the western slope, relatively little to the eastern side, though 
considerable snow does accumulate at high elevations on account of 
the long duration of the cold. As the winds descend the east slope, they 
are warmed and consequently are able to evaporate moisture from the 
ground. The lower eastern slopes therefore are quite arid, except in 
the section near Mono Lake where the range base stands 7,000 feet and 
more above sea level. In the northern Sierra Nevada, the crest is con- 
siderably lower and more moisture is carried over to the eastern side, 
though again the lowest slopes are quite dry. 

Dry summers are characteristic of the range. Little rain falls for 
periods of two or three months, but occasional thunderstorms occur, 
which generally are of short duration. 

Most of the streams draining the range run roughly at right angles 
to its trend, that is, they flow south of west on the western side and 
north of east on the eastern side. There are some exceptions; for 
example, part of the course of the upper Kern River, the head of the 
Middle Fork of the San Joaquin River, Granite Creek and Chiquito 
Creek which parallel the crests of peaks. Because the divide between 
the eastward and westward flowing drainage is roughly the crest of 
the range, eastern streams are short and western are long; most of 
the ea.stern streams are comparatively small because of less available 
supply of water, and most disappear either within the lower parts 
of their canyons or very quickly after they emerge onto the desert 
basins at the base of the range. The principal exception is the Truckee 
River, flowing from Lake Tahoe and emptying into beautiful Pyramid 
Lake which lies in a desert basin more than 30 miles northeast of Reno. 
Some streams flow into Mono and other lakes in the section where the 
range base is at highest elevation, and Owens River, fed by Sierran 
tributaries, flows southward into Owens Lake. 

The heavy concentration of precipitation on the western slope of 
the Sierra Nevada gives its streams much greater volume, though 
there is notable fluctuation caused by the dry season during summer 
and fall. The western streams, with the exception of the Kern River, 
are tributary either to the San Joaquin River in the southern part of 
the Great Valley or to the Sacramento in the northern part. These two 
trunk rivers join not far from Carquinez Strait, the single opening 
in the mountainous rim surrounding the Great Valley, and flow into 
San Francisco Bay. The Kern River is kept from joining the San 
Joaquin by a great barrier of sediment in the southern part of the 
San Joaquin Valley and flows into Tulare basin formerly occupied 




by a large, shallow lake, most of which has been drained to develop 
agricultural land. 

The principal rivers flowing down the western slope, named in order 
from south to north, are the Kern, Kaweah, Kings. San Joaquin, 
Tuolumne, Stanislaus, Mokelumne, American, Yuba, and Feather. 
In the upper reaches of the range, these streams are formed by the 
union of large as well as small tributaries, so that we find the Middle 
and North Forks of the Kings, and similar divisions of the others. 

Because of the high elevation of the Sierra Nevada and sufficient 
slope in both directions from it. the main streams and their tributaries 
have cut narrow canyons. On the eastern side, the gorges are deep to 
the base of the range, but on the western side, the lower part of the 
range has quite gentle slope and consequently valley depth becomes 
much less. Some of the canyons in their headward parts range from 
2.000 to 7,000 feet deep. The Tuolumne and the Kern, for example, 
are 4,000 to 5,000 feet deep in places, and the Kings and some of its 
tributaries measure 6,000 to 7.000 feet. On the western slope, the 
canyons are separated by considerable stretches of rolling upland, 
while between the gorges cutting the steeper eastern side, there are 
sharp-crested, narrow ridges. 

Evolution of the Mountains 

Mountains and mountain ranges are evolved in four principal ways : 
(1) by deformation, which is responsible for the principal eminences 
of the continents and larger islands; (2) volcanic action, which has 
produced some of the most conspicuous and splendid peaks of the 
lands and the only type of mountains rising above sea level from the 
floors of the very deep oceans; (.3) erosion; and (4) deposition. 
Volcanic mountains are formed either by deformation of the surface 
as volcanic rock is forced into the outer part of the earth, or bj- 
eruption, which builds volcanoes and plains on the surface. Streams 
are principally responsible for erosion mountains, which in regions 
high above sea level may be mighty features of the relief. Deposition 
mountains are better termed hills and ridges; generally they are quite 
low, though some sand dunes rise a thousand feet above their base. 

In terms of the length of earth history, mountains and mountain 
ranges, the most conspicuous features of the landscape, are relatively 
ephemeral, being built at various times and then destroyed. At many 
places in the earth, there is record of ranges great and small which 
have been worn down to rolling plains, with perhaps a few higher 
eminences, and then buried by hundreds of feet of debris deposited 
partly below and partly above sea level. The development of principal 
mountain ranges either by deformation or volcanic action is a revolu- 
tionary event because of the profound changes in rocks, rock structures, 
and relief which take place ; but, as with all revolutions, many or most 
of their effects are later wiped out. From time to time parts of many 
ranges may be rebuilt and their span of life thus increased, but finally 

even these rejuvenated sections are subdued and their former presence 
is proved only by certain rocks and rock structures which remain. 

Deformation mountains are of three types, the principal being 
fold-fault ranges evolved by compression of long, narrow belts of the 
earth's rocky shell with consequent abundant folding and faulting. 
The major and most of the minor ranges of the continents and large 
islands are of the fold-fault variety, and some very important groups 
rise from the floor of the shallow ocean, as for example the great island 
galaxy off the west shores of Asia and Australia. Also, there are fold 
mountains, which are more or less simple anticlinal domes, usually of 
small size and moderate height, like the Kettleman and Elk Hills in 
the southwestern San Joaquin Valley. Fault mountains are blocks of 
the rocky shell bounded by faults along which they have been elevated, 
generally with some tilting. 

The Klamath Mountains, the Sierra Nevada, the Transverse and 
Peninsular Ranges, and ranges of the Basin-Ranges province of eastern 
and southeastern California were originally fold-fault mountains, but 
they were built so long ago that they have been re-elevated on various 
occasions after erosion had greatly modified their initial topography. 
The Coast Ranges, on the other hand, are fold-fault mountains which 
have been created during the last half million or million years. 

Evolution of the Sierra Nevada started perhaps 120 or 130 million 
years ago, when, in the late part of the Jurassic period, the western 
half of a great debris-filled trough or geosyncline was crumpled into 
mountains. The oldest rocks known from the Sierra Nevada belong to 
the Silurian period and are about 330 million years old ; but there is 
plenty of indirect evidence, though not in the Sierra itself, which 
suggests that the geosyncline existed long before. The youngest forma- 
tions involved in the deformation are late but not latest Jurassic, and 
were laid down in an ocean. Therefore it is quite possible that the first 
ridges of the ancestral Sierra Nevada appeared as islands projecting 
above this sea and later were welded into more continuous land. 
Compression was intense, so that once-horizontal layers are now steeply 
inclined and broken by great numbers of faults. Magnificent sections 
of the formations showing both sedimentary and volcanic rocks may 
be seen along Highways 40 and .50 traversing the Sierra Nevada, along 
Highway 24 following the canyon of the Feather River, and along 
Highway 120 leading from Mariposa to Yosemite National Park. There 
are of course good sections in many other places, most less accessible. 

How far the belt of Jurassic deformation extended is not definitely 
known. Some believe that it included most of California, western 
Nevada. Oregon. Washington, and much of British Columbia, even 
extending into Alaska and Lower California. Others think that con- 
siderably less territory was affected. Much of the belt has been very 
deeply eroded since the deformation, covered by deposits of later age, 
and broken to pieces by more modern faulting. 



[Bull. 158 

Those who have studied the Sierra Nevada think that the Jurassic 
fold-fault mountains were not particularly higrh — perhaps 6,000 or 
7,000 feet maximum. 

Prior to the building of the Sierra Nevada fold-fault ranges very 
different geofrraphy existed. West of the present California coiist there 
was a long land area or .series of land areas known as Cascadia which 
extended for some distance into the eastern part of what is now the 
Pacific basin. Until late in Cenozoic time, Cascadia was the principal 
erosion area in this part of America, for it stood higher than most of 
the land stretching off to the east. This picture strikingly contrasts 
with that of the present, for Cascadia no longer exists and the great 
mountainous belt from the Pacific Coast to the Rockies has become 
the principal center of erosion. Streams flowed down the eastern slope 
of Cascadia either across lowlands which lay at its base or into shallow 
oceans which spread from time to time over these plains. For a very 
long period, the low country fronting the land now gone was a basin 
of deposition, though at times accumulation of sediment was inter- 
rupted and erosion modelled the deposits which had formed. Also there 
were important volcanic cycles when immense quantities of lava were 
poured out and fragments were violently blasted from volcanoes. Part 
(if these eruptions occurred below sea level and part above. This com- 
plex history is recorded in the multitude of rock layers and rock 
ma.sses found in the mountain ranges of the state ; the time involved 
extended from before the beginning of the Paleozoic era to the end of 
the last epoch of Cenozoic time, very likely including more than a 
billion years. 

Probably a shallow trough-like depression was first formed by de- 
forni.1t ion along the margin of the Ca.scadian highland. This depression 
was enlarged and deepened by the load of .sediment accumulated 
within it, which generated stresses in the weak zone below the crust, 
causing solid outflow of material from beneath the belt of maximum 
deposition. Eruption of volcanic material onto the surface within this 
belt also aided evolution of the trough. Eventually thousands of feet 
of sedimentary and volcanic deposits were formed. The sediments and 
remains of life buried within them show that most of the deposits 
were accumulated under the ocean which in few places was deeper 
than 600 feet at any time and over most of its extent was much shal- 
lower. From this evidence it is clear that, while the base of the trough 
sank many thousands of feet (the total thickness of the deposits is not 
kno«ni but certainly exceeds 30,000 feet in many places), the upper 
surface when below sea level sloped gently from the water's edge to 
very shallow depths. This was part of the continental shelf, which is 
the continuation of land under the ocean to where slopes increase and 
lead to the floor of the deep ocean. When the shelf rose above sea level, 
it rarely stood more than a few hundred feet high. A sediment-filled 

trough of huge dimensions evolved in the fashion described above is 
called a geosyncline. 

Over the continental interior east of the geosyncline deposition of 
sediment was much lighter and the surface of the rocky shell in con- 
sequence was not depressed so far. 

As weathered rock was removed from Cascadia, that land was 
gradually lowered, but from time to time, deforming forces elevated 
it, accelerating the erosive and increasing the ruggedness 
of its relief. Some sediment came into the geosyncline from other bor- 
dering lands, but the coarseness and mass of the deposits adjacent to 
Cascadia clearly prove that region to have been the prime source 
of the debris. 

Geological evidence shows that accumulation of sediment and vol- 
canic material in a geosyncline continues, though not without inter- 
ruptions, for tens or even hundreds of millions of years. Fossils present 
in strata in the Sierra Nevada and in other California mountains 
clearly show a span of about half a billion years, and there are rocks 
long antedating these strata containing indirect evidence of life but 
no actual fossils. Deposition in a geosyncline is always voluminous 
but never continuous. From time to time the sea bottom is lifted out 
of the ocean to form low plains which suffer some erosion though they 
also may receive a veneer of continental sediment or volcanic rocks. 
Proof of such interruptions is clearly shown in breaks separating the 
various formations exposed in the mountains. 

Although deposition in a geosyncline may go on for an immensely 
long period, it eventually ends; these troughs are weak belts in the 
crust because they contain so much unconsolidated or poorly consoli- 
dated debris and consequently they are rather easily deformed. Even- 
tually the trough yields to the stresses constantly at work in the earth 
and begins to buckle and break. In a large section of California this 
happened more than a hundred million years ago. The rocks were 
folded into great arches called anticlines and troughs called s)/nclines; 
also they were broken apart by faults of various sizes along which 
minor or major dislocations occurred. The architecture of the earth 
in this region was revolutionized, for, previous to the deformation, 
most of the rocks had been more or less nearly horizontal sheets. The 
growing ridges were upfolds and blocks bounded by faults and between 
them lay basins or troughs which were downfolds and fault blocks. 
Such a mountainous complex is called a fold-fault system. Sections 
which have been re-elevated in recent time are the Klamath Mountains 
of northwestern California, the Sierra Nevada, part of the Tran.sverse 
Range? east of Los Angeles, the Peninsular Ranges in the southwest 
corner of the state, and some of the fault block ranges lying beyond all 
of these mountains and extending across the Nevada border. 




The deformation of this belt did not proceed without interruption, 
for there were times of frreater activity separated by times of relative 
quiescence. None the less, over a relatively short jjeolojrical interval — 
a few million years — in the later part of the Jurassic period, the 
building of the initial ranges was completed. The height of these 
mountains is not kno\m, but it was considerably less than that of the 
highest part of the Sierra Nevada today; the principal peaks may 
have stood 6.000 to 7.000 feet above sea level but probably not 
much more. 

During the disturbances resulting in the deformation of a geosyn- 
cline into mountains, major changes go on within the heart of the 
folded belt. Not only are the rocks bent and broken by the stresses 
exerted upon them, but those at some depth below the surface are 
metamorphosed ; that is. they are partially or completely reerystallized. 
and new minerals and structures develop. Furthermore much igneous 
activity is initiated. The igneous mechanism is extraordinarily compli- 
cated and may be contained entirely below the surface as appears to 
have been the case during the deformation which produced the Jurassic 
mountains in California. There is no field evidence so far discovered 
that surface eruptions took place during this time, although there had 
been many before the folding began. As has happened in so manj- 
similar settings, an enormous body of granitoid rock developed a mile 
or more below the surface. The folded belt undoubtedly was invaded 
by liquid rock which evolved at still greater depth, but considerable 
sections of the granitoid mass appear to have been formed by the 
remaking of other rocks by volcanic gases and solutions into new 
material which cannot be distinguished from that formed during the 
crj-stallization of a molten mass. This process of remaking other 
igneous * and sedimentary rocks into rocks definitely of granitoid 
character is called granitization. 

Igneous action, like deformation, was not continuous but rather 
occurred in a series of waves, for many bodies of granitoid rook have 
been differentiated in the Sierra Nevada, all apparently belonging to 
the same volcanic cycle. Some bodies transgress others, showing that 
they are slightly younger. In other words, the total body which is 
called a batholith or deep-seated igneous intrusion, was formed over 
a considerable time and consists of many parts, only a few of which 
have so far been separated. 

Granitoid rock like that composing the Sierran batholith includes 
true granite and other rocks closely associated in chemical and mineral 
composition. They have been formed probably at depths of at least 
a mile below the surface. For this reason the growth of crystal grains 
has been relatively slow and the rocks are generally medium- to coarse- 
grained. They are characteristically light colored, grray being the 

• Igneous rocks have soltdifled from molten masses. Sedimentary rocks have been 
formed chiefly from waste products of other rocks or from organic debris, or by 
chemical precipitation in water. 


dominant shade. The rocks are made to a very large extent of two 
light-colored minerals, one called quartz and the other feldspar. 
Quartz is a mineral of simple composition, always being composed of 
one part of silicon and two parts of oxygen ; feldspar, on the other 
hand, is represented by several varieties, each much more complex in 
composition than quartz. In most granitoid rock, there is a distinctly 
minor quantity of the dark-colored mineral grains that give the rock 
its pepper-and-salt appearance. These dark-colored minerals contain 
various proportions of iron and magnesium while the light-colored 
varieties do not. 

The volcanic cycle apparently started during the deformation in 
the late Jurassic and continued after it. possibly into the earlier 
part of the Cretaceous period. When finished, a gigantic rock com- 
plex was evolved entirely under the surface. It probably extends 
throughout the folded belt and, in the Sierra Nevada at least, evi- 
dence derived from study of earthquake waves indicates that it is 
10 to 12 miles thick. Round about the margins of this great mass, 
the covering rocks were intensely metamorphosed into new types, the 
metamorphic eflFects decreasing with distance from the batholith. 
The granitoid rock is very resistant as are most of the metamorphic 
rocks. Closer to the surface where the metamorphism did not reach 
and where the rocks of the geosyncline were less thoroughly consoli- 
dated, the materials were weaker and more easily weathered and 
eroded. The development of the granitoid core and its associated zone 
or aureole of metamorphic rocks thus increased the strength of the 
heart of the deformed belt. 

The Sierra Nevada of today is very different and much more 
majestic than the ancestral ranges of Jurassic time. Instead of being 
a series of elevated ridges separated by troughs and basins, it is now 
a gigantic tilted fault block so huge that within it are a number of 
minor ranges, each of considerable magnitude. The eastern face of 
this immense block is a scarp developed along a multitude of fractures 
called faults. A fault is a break in the outer earth along which the 
adjacent blocks slip past each other. The western side of the Sierra 
Nevada is a complex of landscapes evolved during the long interval 
since the birth of the original fold-fault system. 

Understanding of the many changes which have occurred in Sierran 
landscape requires a brief analysis of what has transpired since the 
mountains first appeared. Because the size of the range is so great and 
its geologj- so complex, at present it is possible only to outline the 
principal steps in the story. 

Between the end of the first rise of the system and the close of 
Cretaceous time, nearly 60 million years elapsed, but of this interval 
there is only the scantiest record. By the beginning of the last or 
Cenozoic era. another 60 million years a^o. the ranges had been so 
eroded that they were quite inconspicuous, and in places the ocean 



[Bull. 158 

spread to their western base. The land was so low that winds sweeping 
inland from the Pacific Ocean did not lose most of their moisture over 
Sierran slopes as they do todav. Instead they provided enoujjh rain 
for hundreds of miles inland to permit the frrowth of a luxuriant 
vefjetation which could not possibly exist over most of the reyrion 
under the arid conditions that now prevail. This is proved by the 
character of fossil plants found in deposits belonging to that time. 

During the Eocene, first epoch of the Cenozoic Tertiary period, the 
region was bowed upward along an axis approximately that of the 
present Sierra-Cascade system. A low mountain barrier was created 
and fairly deep gorges were cut into the rising hills. The shore line 
still remained close to the present western base of the Sierra Nevada. 

During Miocene time, however, the mountains had been elevated 
sufficiently to cut off most of the moisture and the region to the east 
became arid. 

Much more vigorous disturbances marked the end of the Miocene 
and the beginning of the Pliocene epochs, for the Sierra Nevada was 
elevated considerably and became strongly unsymmetrieal in form 
with a broad western and short eastern slope. There was much fault- 
ing and associated volcanic activity. Faulting conspicuously increased 
the boldness of the eastern slope, especially north of Mono Lake where 
several long range spurs were developed. Between one of these spurs, 
the Carson Range, and the main Sierra Nevada, a section sank, evolv- 
ing the basin now partly occupied by Lake Tahoe. Faults also broke 
the western foothills, so that the long slope in places descends in a 
series of abrupt steps. 

Then followed a period of relative calm during most of Pliocene 
time and erosion dominated over elevation by deformation. Con- 
siderable changes in the landscape of the range resulted. But the 
quiescence was not enduring, for at the end of the Pliocene and con- 
tinuing into the earlier part of Pleistocene, the deformation was vigor- 
ously renewed. These movements lifted the Sierra Nevada approxi- 
mately to its present height and the country to the east also was 
elevated .so that Owens Valley stood about 9,000 feet above sea level, 
considerably above its present maximum height. Most of the elevation 
took place before the beginning of the Pleistocene or Glacial epoch 
so that the snow and ice which remained year after year was bulky 
enough to generate the slowly moving ice masses called glaciers. Rec- 
ords of profound glaciation recognized as belonging to the earliest part 
of Pleistocene time have been found, hence the region must have been 
nearly as high as now for, even during the climaxes of the glaciations, 
the snow line in the Sierra Nevada apparently did not lie much below 
11,000 feet. 

Most convincing evidence left by an early glacier is provided by 
the debris deposited on the mountains west of McGee Canyon. The 

principal glaciers on the cast side of the Sierra Nevada, because of 
the steepness of its slope, were vnllcy glaciers, that is they formed in 
valleys or canyons which already had been eroded by rivers. Moraines 
are great heaps of unassorted rock fragments, some of which are very 
large. Valley glaciers leave two principal types, the more common 
side moraines formed from debris frozen in the sides of the ice and 
carried on its top, and terminal moraines, compo.sed of rocks and fine 
sediment pushed in front of the ice and melted from its end. 

The McGee moraine, which has been identified as belonging to the 

first of the four glacial stages, ends abruptly at the great eastern scarp, 
and stands about :?,000 feet above Long Valley at the base of the scarp. 
Study of the moraine .shows that its glacier followed a rather flat, shal- 
low valley high in the Sierra Nevada, proving that McGee Canyon anfl 
the scarp into which it has been cut did not exist. Moreover the McGee 
moraine, in spite of some later damage, obviously was about as large 
as the moraines of the later glaciers. This, together with much other 
evidence, indicates that the Sierra Nevada had about as large an ice 
mantle during the early Pleistocene as it did later in the epoch. 

Abundant evidence indicates that the ea.stern scarp does not owe 
its height to elevation along faults at the base of the range. Rather, 
long, narrow blocks sank, developing Owens, Carson, and other valleys 
immediately east of the range. These depressed masses were broken 
into great numbers of fragments by lesser faults and along them there 
has been much volcanic eruption. On the other hand there is not much 
evidence of shattering within the main mass of the Sierra Nevada at 
the time of the last disturbance. 

Other proof that the depressed blocks have sunk is afforded by the 
slant of the lowlands toward relatively fresh fault scarps. At the base 
of the range and against these scarps is either wet, swampy land or 
lakes, such as Owens Lake, which is deepest near its western shore 
against the highest section of the Sierran scarp ; the wet meadows 
sloping to the range base near Bigpine; Mono Lake, lying next to 
a steep scarp and deepest on its western side; the marshes in Carson 
Valley which lie directly beneath fresh fault clilTs at the base of the 
Carson Range ; and Honey Lake at the far northern end of the scarp. 

The giant scarp, without doubt the most magnificent example in 
America, thus is not much over 800,000 years old and has been increas- 
ing in majesty as the bordering, eastern blocks have continued to sink. 
It has been considerably battered, for a multitude of deep gorges have 
been cut into it and the upper parts or even the entire length of many 
of these gorges have been glaciated. 

Faulting at the base of the range has occurred intermittently, some 
of it being very recent. Very probably there have been differential 
movements along the faults so that the Sierra Nevada has risen some- 




what but its height has not been yrreatly increased over that developed 
by the late I'liiH'ene-early I'leistocene deformation. 

Farther east in the Basin-Ranjres province, similar faulting sepa- 
rated formerly continuous stretches of landscape, raising some to 
form ridges and ranges, and depressing others to form troughs and 
basins. Some of this faulting to the east started as early as Miocene 
time, some is of much later, and some is going on actively today. Of the 
blocks which were isolated by faulting, the Sierra Nevada is by far 
the largest. It must not be supposed that the great fracture systems 
bounding the blocks were developed quickly or that the immense dis- 
locations were accomplished in brief intervals. Rather, the faults grew 
in length and complexity and the individual movements along them 
were relatively small, a few feet to a few score of feet. Furthermore, 
there is no evidence that dislocations occurred along the entire length 
of a fault system at the same time. 

There is much additional information about the growth of the 
Sierra Nevada contained in F. E. Matthes' entertaining book. The 
Incomparable Valley, compiled after his death by Fritiof Fr>-xell. 
Much of the foregoing story of the later history of the range is sum- 
marizetl from this volume. 

As the up-arching of the Sierran region went on. the maximum 
elevation was attained in the northern half of the southern section. 
Very possibly this height is being slightly increased while the adja- 
cent valley blocks are still sinking. 

Eastern Fault Scarp 

In places, as along most of the western side of Owens Valley, the 
principal fault bounding the eastern base of the Sierra Nevada appears 
to be relatively simple and most of the movement was concentrated 
along it. Along most of the range, however, intersecting fractures 
are indicated by salients and re-entrants like those west of Bishop 
near the head of Owens Valley. Also, there are many faults parallel 
to the main system along which blocks have sunk less than the valley 
blocks, producing a terraced front. South of Mount Whitney, there 
seems to be no actual evidence of faulting along the base of the range, 
but its form definitely suggests that this portion as well is a tilted 
fault block. The fracture zone appears to have been completely buried 
by great masses of sediment carried from canyons worn into the fault 
scarp. The faulting in this southern section appears simple for there 
is little evidence of the step-blocks that produce a terraced front. 

The great scarp is highest and most clearly defined from Olancha 
at the southern end of Owens Valley to Independence, for the abrupt 
descent from the crest of the range is not broken by any foothills. 
Striking faceltd spurs, the truncated ends of ridges broken by the 
faulting, may be seen south of Owens Lake but are larger and bolder 
southwest of Independence. The east .slope of Mount Williamson, 
dominating peak of the Sierra Nevada visible from this part of Owens 

Valley, is a huge triangular facet into which have been cut three 
lesser facets. Each of the three rises to a height of 10,000 feet, below 
which the range slope shows the marked over-steepening characteristic 
of recently developed fault scarps. 

West of Independence, the Sierran scarp changes in contour. The 
base exhibits salients and re-entrants formed by granite foothills pro- 
truding through the deposits at the base of the range and apparently 
lying against its main mass along the principal fault system. These 
foothills doubtless are step fault blocks which either have not sunk 
as far as the Owens ^'alley graben or have not been elevated as far 
as the main block. 

Farther north toward Bishop, fine triangular facets again appear 
indicating that the boundary fracture is a simple one. As far north 
as Birch Mountain, the eastern side of the Sierra Nevada presents 
unmistakable proof that it has been developed by profound dislocation 
along the fault system, but from there northward to Bishop Creek, 
the evidence is less convincing. Long, straggling foothills project into 
Owens Valley and merge with the main mountain mass. In this section, 
there probably are a number of parallel faults, with the dislocation 
distributed more or less equally along them through quite a wide zone. 
There has been sufficient erosion to obscure most evidence of faulting, 
a common occurrence where this step structure is present. 

In the ^^cinity of Bishop Creek, the fault system is offset to the west 
about 8 miles in a manner characteristic of the area farther north. 
The scarp here shows the same abruptness and simplicity as near 
Owens Lake ; the best development is the extraordinarily steep slope 
facing Round Valley. The fault indicated by this declivity, if pro- 
longed southward, would coincide with the canyon of the South Fork 
of Bishop Creek, which is conspicuous among the canyons on the east 
side of the Sierra Nevada in having an approximately northward 
trend. There is good evidence that this canyon has been developed by 
faulting. The fact that an advanced erosion surface standing 2,500 
feet above the river in the bottom of the canyon is at essentially the 
same elevation on both sides of the canyon indicates that this gorge, 
if evolved by faulting, is a rift valley: that is, its floor is a block which 
has sunk between two faults. An oiled road leads up this valley from 
Bishop to the beautiful glacial lake country on the east side of the 
high Sierra. 

Multiple displacements along both sides of Truckee Meadows have 
formed this (jrabeii,' which has hill areas projecting above its surface. 

North of the Truckee River, the faulting and therefore the Sierran 
front change notably. Displacement along the boundary fault dimin- 
ishes, the faulting apparently is multiple in many places, and north- 
ward-trending ridges project from the main mass of the range. 

• A graben is a basin or trough formed by sul>sidence of a block or blocks of the 
earth's crust along faults. 



[Bull. 158 

>?P^> —', -^^$=0^ 

Vk.. 4. Lake Talioe (background). Fallen Leaf Lake (left foreground) occupies a basin formed by a terminal moraine left by a valley glacier that 

came from the Pyramid Peak area. Photo hy courtety U. S. Army Air Corps. 




Fig. 5. Section showing fault scarp north of Kern River, 
east of Bakersfield. After G. K. Gilbert, V. S. Geol. Surrey 
Prof. Paper toS. p. 88. 
Tahoe Basin 

The outstanding example of the effect of faultin<r within the Sierra 
Nevada is the Tahoe basin, which lies near the crest in the central part 
of the range and is partly occupied by Lake Tahoe. This lake, by far 
the largest in the Sierra Nevada and the major body of water in the 
state, is nearly 22 miles long. 12 miles across at its widest place, and 
has a depth of more than 1.600 feet. Its surface stands a little over 
6,200 feet above sea level. On the eastern and western sides of the 
basin are rugged mountains whose summits are from 8.000 to 10.000 
feet high; Rubicon Peak (9.193 feet) and Mount Tallac (9,785 feet) 
are the principal eminences on the western rim. In the Carson Range 
on the east side. Mount Rose rises 10,800 feet and Genoa Peak 9,173 
feet. This eastern range slopes less abruptly toward the basin than 
does its western counterpart and therefore looks lower, but it is not. 
The two ranges completely enclose the low region between. 

It is the common belief of people living or visiting at Lake Tahoe 
that it is of volcanic origin, but such is not the case. The general 
features of its evolution are well kno^vn, though many details remain 
to be supplied. The basin has been formed by dislocations occurring 
at the time of the vigorous Miocene-Pliocene deformation. Two prin- 
cipal faults, one on the east and one on the west side of the basin and 
both roughly parallel to the great boundary fault .system at the eastern- 
base of the range, evolved as the Sierran region began its upward 
movement. The Carson Range, forming the eastern rim of Tahoe basin, 
rose along the boundary fault while the mountains on the west were 
elevated along the fault on that side. The intervening area slowly and 
unevenly settled evolving the Tahoe basin and Sierra Valley farther 

Because of the heavy snows and rains in the region, a lake quickly 
formed near the southern end, or lowest part of the graben. Since the 
passes through the bordering ranges stand at considerable elevations 
above the basin floor, the lake grew to much greater size and depth 
than it now is. Finally its water found an exit through a low spot 
in the Carson Range not far of the present site of Truckee and 
the Truckee River was born, pouring down the eastern slope of the 
Sierra Nevada. This stream began to excavate a gorge mostly in 
unconsolidated volcanic debris. Highway 40 follows the course of the 
Truckee River in going down the eastern side of the Sierra Nevada. 
As the canyon was deepened, the level of Lake Tahoe gradually fell 
and its area diminished. 

Somewhat later basalt flows were erupted, flowing into Truckee 
Canyon and forming a dam extending to the present northern end 
of the lake which for a time broke the Truckee River. Finally the lake 
overflowed this barrier, cut a gorge through it, and the river was 
re-established ; the flows of lava can be clearly seen in the walls of the 
gorge along the highway leading to Lake Tahoe from the north. 

The Truckee River flows from its canyon at the eastern base of the 
Sierra Nevada across desert fault basins until it empties into Pyramid 
Lake which occupies one of these basins some 30 miles northeast of 
Reno, Nevada. 

rock slope 

Joint surfaces 
and terraces 

Flo. 6. Idealized sketch of the fault scarp which extendi 
for about five miles north and south of the Kern River Oan.von 
east of Bakersfield. .After O. K. Gilbert, U. S. Geol. Surrey Prof. 
Paper 153, p. 86. 




[Bull. 158 

The southwestern side of the Sierra Nevada is sharply contrasted 
in dimensions, slope and topofrrajihy with the great scarp fronting in 
the opposite direction. Only in one place for a distance of about 5 
miles north and south of the Kern Kiver canyon east of Bakersfield 
in the San Joaquin Valley is the western base defined by a fault. Else- 
where, except for minor effects produced by faulting, the southwestern 
side slopes gradually to its base where it passes under sedimentary 
deposits which in places in the Great Valley to the west are very thick. 

At the mouth of the Kern River canyon, the base of the Sierra 
Nevada is a nearly straight face of granitoid rock broken into tri- 
angular facets by young gorges which cut it. The scarp is about 400 
feet high and 5 miles long. Actually it is not a single surface, but is 
made up of several steep declivities separated by narrow inclined 
terraces that evidently are controlled by jointing which is prominent 
in the bedrock. The steep sections of the scarp exhibit little evidence 
of faulting for they have been too much weathered. There does, how- 
ever, appear to be a vertical grooving best seen at a little distance and 
many patches of small quartz veins are vertically fluted in harmony 
with the larger grooving. Probably the various elements composing 
the main scarp were originally a single fracture surface, and have 
since been separated by slippage along the joints, developing a minor 
type of step faulting. On the north side of the Kern River canyon, the 
lower part of the scarp is much steeper and smoother than the upper, 
indicating close approach to the slope of the actual fracture surface, 
the upper part having been more eroded. 

The narrow terraces which break the continuity of the scarp are 
roughly parallel and rise from north to south across it. They are 
covered to some extent by soil and waste which has fallen from above. 
At the base of the scarp are considerable deposits from the face and 
brought out from the canyon of the Kern River. The fault evidently is 
recent but no movement is known to have occurred along it in his- 
toric time. 

This rift certainly does not mark the western boundary of the 
Sierran block, rather it is a local feature. Location of the western 
boundary is not known but possibly it may be against the Coast 
Ranges on the western side of the Great Valley. It has been proved 
that Sierran bedrock extends under deposits in the Great Valley which 
in places are very thick, but the bedrock has only been met where the 
overlay of sediment is much thinner. As more deep oil wells are drilled 
and particularly as more geophysical prospecting is done in the Great 
Valley, knowledge of the extent of the Sierran block below the valley 
will be extended. 

The foothills of the Sierra Nevada rise from the border of the Great 
Valley as a series of low hills and ridges increasing in altitude and 
elevation above their surroundings as the main range becomes higher. 

The higher ridges in the foothill belt are formed by the more resistant 
members of the Sierran bedrock complex while the weaker members 
form low hills having rather gentle contours. Between these eminences 
are narrow ridges and winding valleys. East of the foothill belt, the 
ridges and hills are more prominent and the canyons are deep and 

Fig. 7. Old erosion near Kaweah Canyon. Photo by CordcU DurreU. 

Between the great canyons which are such prominent features of 
the western side of the Sierra Nevada are extensive stretches of rolling 
upland that become increasingly rugged in the higher parts of the 
range. In these uplands remnants of two principal landscapes so far 
have been recognized. 

To understand the development of this ancient relief, it is necessary 
to trace changes which have occurred since the Jurassic fold-faulting. 
When the Sierra Nevada was first built, it consisted of a series of 
roughly parallel ridges separated by troughs or basins, ail outlined 
by the deformation. The principal rivers flowed through these troughs, 
here and there breaking across or flowing around the ridges and 
eventually passing beyond the mountain belt. Minor streams descended 
the ridge slopes, either joining the trunk rivers within the range or 
flowing beyond the mountains to add themselves to other drainage. 
Such a stream pattern is found today in the Coast Ranges, which 
were formed by fold-faulting in middle Pleistocene time. 

By the end of the Cretaceous period, the Sierra Nevada had been 
worn down to relatively low elevations so that its highest points were 
not much more than 2,000 or 2,500 feet above sea level. Early in the 
Eocene epoch, the range seems to have been gently upwarped along 




an axis rouf?hIy coinciding with its present crest ; whether a corre- 
sponding slope increase took place on the eastern side we do not know, 
for later events have obscured too much of the record. As a result, 
there was considerable rearrangement of drainage, for southwestward- 
flowing streams grew at the expense of streams oriented in other direc- 
tions, becoming trunk lines which divided among themselves many 
rivulets that had been flowing parallel to the trend of the range. 
In the latest part of the Eocene and part of the following Oligocene 
epochs, there was an alteration of erosion, deposition, and volcanic 
eruption which altered the landscape, but subsequent modifications 
have wiped out most of this record. 

The Oligocene activity was followed by a long interval of virtually 
uninterrupted erosion which developed toward the end of Miocene 
time the older of the two landscapes found in the roUing country 
between the great canyons of the western slope. The highest peaks 
had been reduced to elevations of little more than 6,000 feet above 
sea level and were located principally where the crests of the Sierra 
Xevada are today ; most of the peaks were aligned in roughly parallel 
rows as we now see them and these rows probably represented the 
greatly modified ridges formed during the Jurassic fold-faulting. 
In the northern part of the Sierra Xevada there are enough remnants 
of the deformed bedrock in many places to indicate this clearly. 
In the southern two-thirds of the range, however, erosion had removed 
the bedrock and was working in the great granitoid batholith below; 
nevertheless, the rows of peaks clearly show that their position is 
controlled by structural ridges which once lay above the batholithic 

The peaks of Miocene time were far from startling, rising only 1,500 
to not much more than 2,000 feet above rather broadly flaring canyons 
that separated them. Their tops were mostly flattish or rounded and 
their slopes were only moderately steep. Farther down the western 
slope of the Sierra Xevada the landscape was still more subdued. 
Ridges from 500 to a little more than 1.000 feet separated flat valleys 
which increased in width toward the lower part of the range. The 
streams flowing in these valleys had reached maturity and had eroded 
terraces into the bedrock. Some of the ridges rose quite abruptly 
from the outer margins of the terraces while those in less resistant 
rock ascended with gentler slopes. Most of the streams flowed south- 
westward as they do today, but som? followed depressions between 
the rows of peaks as they had done in the early stages of the develop- 
ment of the range. An example Ls the upper part of the Kern River 
which parallels the trend of the range between the eastern and 
western crests before it finally breaks across the latter to descend the 
western slope. 

This stage in the evolution in Sierran landscape has been called the 
hroad valley stage; remnants are recognizable in many places, par- 

Fig. 8. Bird's-eye view of the Yosemite V;illey as it proli.alily wns in the hrcid- 
valley stage, prior to the first great uptilting of the Sierra Nevada. The Merced 
River meandered sluggishly over a broad, level valley fltwr flankeil by rolling hills 
between .")00 and l.CKHI feet in height. The crown of El Capitan sIixhI alwut 0(10 feel 
high. There were no cliffs or waterfalls. The tributary streams all sloped gently down 
to the level of the Merced. The entire region was ctivered with dense rain-loving 
vegetation. RC, Kibbon Creek : EC. El ("apitan : KP. Eagle Peak ; IT. Yosemite 
Creek: I(\ Indian Creek: R, Royal Arches: \V, Washington Column: TV. Tenayn 
Creek ; .YD. Xorth Dome : «/). Basket Dome ; .1/ It". Mount Watkins : E. Echo Teak : 
C. Clouds Rest : *■'.)/. Mountain ; II D, Half Dome : -U. Blount Maclure : /.. 
Mount Lyell : E, Mount Florence : HP, Kunnell I'oint : CC. Cascade Cliffs ; lA'. 
Little Yosemite Valley: B, Mount Broderick ; LC, Liberty Cap: SD. Sentinel 
Dome ; SR, Sent.nel Rock : XC. Sentim>l Creek ; CR. Cathe<iral Rocks : BV. Bridal- 
veil Creek : DP. Dewey I'oint : MR. .Mert-e<l River. After E. E. Malthes. f. S. Ueol. 
Surrey Prof. Paper lUO. p. 4tl. 



[Bull. 158 

. X"^-4 '^0':- ><>' >>-^ tv-'-V 

Fio. 9. Itiril's-pye view of thr Yosemife Vnliry ns it probably was in the nmuii- 
tain-vnlley sta^e. after it had liefn (ieeponed about 700 feet by the Merced River in 
consequence of the tirsit ;;reat uptiltiiiK of the Sierra Nevada. The valley was flanked 
by upbiiuls. and Ribbon (.'reek, Ynseniiie f'reek. Sentinel Creek, Britbtlveil Creek, 
and Meacbiw Uronk cax-aded steeply fmni the mouths of hantjinK valleys. Tenaya 
Creek, Illibuiette Creek, and Indian Creek, however, had cut their valleys down to 
the level of the Merced, The re;;ion was covered with mixed forests containing 
sequoias. A/rer F. E. Matthes, V. S. Geol. Survey Prof. Paper J60, p. 41. 


Fig. 10. Bird's-eye view of the Yosemite Valley as it probably was in the canyon 
stage, just before it was invaded by the glaciers of the ice age. The valley had been 
cut 1,300 feet deeper by the Merced River, in consequence of the second great up- 
tilting of the Sierra Nevada, and had a V-shaped inner gorge and two sets of hanging 
side-valleys. Illilouette Creek and Indian Creek now also made cascades, but Tenaya 
Creek and lower Bridalveil Creek had cut gulches down to the level of the Merced. 
The region was covered with coniferous forests adapted to a temperate climate with 
cold, snowy winters. Ajter F. E. Matthes, V. S. Geol. Survey Prof, Paper 160, p. ^8. 




ticularly in the southern part of the range. Naturally they have 
suffered much damage by later erosion and in parts of the Sierra 
Nevada have not been detected, though more thorough study may 
reveal them. 

In late Miocene and early Pliocene time, the northern third of the 
Sierra Nevada at least became a great volcanic field. Frequent explo- 
sions erupted great quantities of coarse and fine debris of andesitic 
lava and a considerable number of flows also were poured out. Jlost 
of the centers of this activity lay east of the present Sierran crest but 
some have been recognized in the crest region. The fragmental deposits 
for reasons that we do not know became waterlogged and moved as 
great avalanches down the valleys piling one upon another as the vol- 
canic cycle continued. Even after much erosion in the crest region there 
are sections of these volcanic mud flows 1.500 to 2.000 feet thick. In 
spite of the relatively low slope of the valleys, the mudflows were liquid 
enough to move through them and in some cases passed the base of the 
Sierra, spreading onto the eastern side of the Great Valley. The valleys 
in the range were well filled and some of the lower ridges were over- 
whelmed but the higher eminences projected above the volcanic sur- 
face. Apparently the mudflows formed a flat area with masses of 
bedrock protruding through it. Certainly this landscape covered much 
of the northern third of the Sierra Nevada but how far south it 
extended cannot be determined as the amount of erosion which has 
since occurred is difficult to estimate. The suggestion is strong, how- 
ever, that most of the southern section of the range lay beyond the 
limits of the volcanic activity. 

After the close of the volcanic episode in the earlier part of Pliocene 
time, the Sierra Nevada which then probably was much broader than 
today was elevated about 3,000 feet. The deformation doubtless was 
not continuous, but was concentrated in certain intervals with others 
of relative quiescence between. The elevation of course increased the 
slopes of the range and the streams were correspondingly invigorated. 
Where they had started to flow on the volcanic surface, they cut 
through it into the bedrock, while others in the broad valleys cut 
young gorges below the surfaces of the terraces which they had eroded 
prior to the elevation. These new canyons were 1,200 to 1,500 feet 
deep by late Pliocene time. The upper part of the Kern River, flowing 
parallel to the crests of peaks, reached maturity while the streams 
descending the steeper western slope were still young, at least through- 
out most of their length. The Kern therefore began to widen its valley, 
destroying much of the terrace which had been cut before the early 
Pliocene elevation. Remnants of the broad Miocene valley are pre- 
served along the sides of the peaks of both eastern and western crests 
but are not particularly conspicuous; none the less it is possible to 
reconstruct the valley approximately. Remnants of the Pliocene 
mature valley are finely preserved as flat areas in the Mount Whitney 

region. Thus there is striking contrast between this longitudinal 
mature valley and the dominantly young canyons of the same cycle 
on the western slope. 

The Pliocene landscape, which is a much more \-igorous one than the 
Miocene, has been termed the mountain valley landscape. The highest 
peaks of the Sierra Nevada at this time seem to have stood about 
6.000 to 8,000 feet above sea level, but most of them had been evolved 
during the still earlier erosion cycle. 

The late Pliocene and early Pleistocene elevation of the Sierra 
Nevada and the region to the east caused a sharp increase in the 
gradient of the streams and therefore in their downcutting power. 
They began the incision of the great canyons like the Yuba, the 
American, the King, and the Kern. Since the range probabh- is sti.ll 
rising to some extent, the canyons are still being deepened ; they are 
narrow. V-shaped gorges with bold, ragged slopes rising abruptly 
from the sides of the streams, except where the canyon form has been 
modified by glaeiation. as in Yosemite Valley. Although these great 
gashes have been speedily eroded because of the considerable increase 
in slope of the western Sierra Nevada and the abundance of water 
available, the elevation has been recent enough so that broad stretches 
of the older landscape remain between them, making it possible to 
read at least part of the chapters of later Sierran hi.story. The canyons 
naturally are deepest in the central, highest part of the range ; to the 
north and the south they are less conspicuous, but are nevertheless 
deep gorges. 

This stage of landscape development, which started on the western 
side of the range in late Pliocene time is called the canyon stage. 
Unlike the others, it is also represented on the eastern side, but there 
the gorges have been slashed into the great fault scarp, most of which 
was formed after the first glacial stage of the Pleistocene epoch. 
Remnants of the older landscapes are not present on the eastern side 
of the Sierra Nevada except in a few places where they have been 
preserved on step-fault blocks. On the eastern side the landscape is 
mostly a succession of deep gorges separated by narrow crested ridges. 

Except for the great fault scarp on the east side of the Sierra 
Nevada and Tahoe basin with its beautiful lake, the most startling 
features of the range are those which have been modeled in part at 
least by glacial ice. snow avalanches, and frost wedging with associated 
fall of blocks of rock. 

To understand the extraordinarj- work of ice in sculpturing the 
high Sierra Nevada requires a brief discussion of the last chapter of 
earth history, the Pleistocene epoch of Tertiarj- time or, as it is com- 
monly called, the Glacial epoch. 

During the last great marine period of earth history, the Cretaceous, 
extensive seas prevailed, and the climate over most parts of the earth 


was much more equable than today — a characteristic of the iropor- practically all of the ice disappeared from the earth. Areas outside 

tant marine intervals. Such climate continued over somewhat reduced of the polar regions were strikingly changed climatically during both 

areas and with some modifications for the next 15 or 20 million years; glacial and interglacial times. 

but, as the continents gradually enlarged, far-reaching climatic mt . ^^ <? .i ,-,, ■ , , , , . , , , 

u » • r^i- •• 1 1 1 c 1 J iu Ihe length oi the ulaeial epoch has been extensively debated bv 

changes set in. Climatic zones were more sharply defined and there ,''.., ., ' „ , , , ui^^-lcu i,., 

„ • • jjr »• •• c ^■ ..■ ^ ITT,., . i J. ^ many authorities, but evidence so far accumulated does not permit an 

was an increasing differentiation of climatic types. While intermediate • ,. ' „ . . , . " "' " ""^= ""■- t"; '"-^ °" 

1 .-. J . • , J J ■ i • 1 1 Ui • 1 accurate estimate, the range ot opinion being from 1 to 5 million years 

latitudes were becoming cooler and drier, tropical and subtropical r, < ,, ^. . ■ ■ , l , ^ >^iii ^ lu u 1^1,111,,, ..^ a, 

• „i,,. V ,; _ v„ , , „„ -J J u • £ J Probably the beginning of the epoch was not more than 2 million 

regions which earlier had been so widespread were becoming confined , , m, > .. p ■ , ■ , , . , . , 

._,.., . ,. ., J ^, r 11, » T iu years back. Uie lengths ot the glacial and interglacial stages also arc 

to a relatively narrow belt north and south of the equator. In the ■' , . , ..,,,, ,,.,,, .... <•->"»<• 

extreme north and south and at high altitudes, cold blanketed larger uncer am. Assuming that the epoch started about 1 million years ago, 

and larger areas. In this progressive climatic change the rise of the *^« following chronology has been suggested : 

continents to abnormal heights above sea level and the extensive First glacial stage 1,000.000-900,000 years 

building of mountains which had characterized late geological time ^'"" interglacial stage 900,000-700,000 years 

played an important role. Other factors, not vet determined, were also Second glacial stage 700,000-600.000 years 

undoubtedly involved. " Second interglacial stage 600,000-325,000 years 

.„^ . „, . , , , .„. , Third glacial stage 325.000-22.->,000 years 

When the Glacial epoch started a million or two years ago, the area Third interglacial stage 225,000-100,000 years 

over which polar climates prevailed rapidly expanded in high and p„„^,^ ^,^^5^, ^^^^^ 100,000 years to present 

moderately high latitudes both north and south-of the equator and at a. Culmination 55,000 years 

high altitudes. Where the climate was glacial, the cold was so intense ^- Beginning of last principal ice retreat 25,000 years 

that a lasting cover of snow and ice began to grow, since all of the 

snow ai'ciimulated during the colder months could not be dissipated 

during the slightly warmer days and weeks. This blanket gradually 

increased in thickness, and from the margins of the larger masses, 

moving fronts or tongues of ice called glaciers were projected. Beyond 

the glacial areas and regions were stretches of the slightly less hostile 

tundra climate where snow and ice melted during a few warmer weeks 'S^V^ 

of the year, and frozen ground was thawed to depths of a very few 

feet. Below this shallow melt-zone, ice extended for scores or even 

hundreds of feet, particularly in the higher latitudes of the northern 

hemisphere and there even today tundra regions are very extensive. ^ N.''^Vk^\J!*nPWnHB\.ii ^i'W -r- , ,. i^»- - 

Under the permanent ice, water also was frozen in the rocks and L- ""x ^''^ ^'J^U-^^''^9!^^-.M'^f^^^^''^^kf^MtK9fi»iv^' 

remained so throughout the year. ^^'^'^v^ij^^BBB.^ ■'^!l>*^!i5%^* * '*'■'* "»' **- "A 

During the Glacial epoch, the climate fluctuated notably over much v V^*' ♦"V^^sBS^J^^ " ''?'.'' 

of the world. Four times the glacial areas expanded, increasing the ^ ■ ' ' , ^^^T*^ 

extent of the lasting mantle of snow and ice until the maximum _ '^ rvjiife-* 

coverage amounted to about 32 percent of the land above sea level. ■ ^" 

These four episodes are the glacial stages, in the last one of which we * S V ^ij^" "- *"UfKl^^KK ^ 

live. Then, for reasons as little known as are the causes of their expan- ,., ,, ..., , ., t.- ., „ , , , , , , • . ., 

' * III.. 11. I li'* v'lii^' ''i'nyon of the feather Uiver hns t).', Ml (l..|i!v eroded into the 

sion, the areas dominated by polar climate shrank, glaciers and other Su-mui,.tk as tiu- result of invigoration of .streams caused by tiie laie I'liocene 

masses of ice receded or disappeared, and warmer conditions developed ''"'^y i*iei«iocene elevation of the region. The form of ihi.s canyon i» typical (.f the 

i. i» ii. 1 J • 1 ,. ij • iu ■ c J.I. ' mu non-glaciated portions of all canyons in the range. /*Ao(o cour/cgu 0/ H'cjfkrn /*aci/ic 

over most of the land previously held in the grip of the ice. The Railroad. 

magnitude of ice recession during these interglacial stages is not 

known, but doubtless it was different in each as also was the magni- If the Glacial epoch includes more than 1 million years, the figures 

tude of advance during the four glacial stages. It is quite probable given above must be proportionately increased ; further studies also 

that, at least during the longest (the second) of the interglacial stages, may revise the proportions between glacial and interglacial stages. 




Two facts, however, are well established. The j^lacial staiires are the 
outstanding features of the epoch, but the interfrlacial stages were 
of considerably greater length. 

Considering the small amount of ice on the earth in pre-Glaeial and 
interglacial time, the creation of the glaciers and other ice masses 
was rapid and on an enormous scale. As previously noted, the maxi- 
mum coverage included at least 32 percent of the land above sea level, 
and in addition areas of the ocean were frozen to depths of a 
few feet or, in some places, as much as a few hundred feet. The 
glacial stage, the one in which we live, witnessed the overwhelming of 
about 27 percent of the land, and of this area more than a third still 
lies beneath the snow-ice blanket. It is dear therefore that the present 
is a brief interval in the waning of a glacial stage, a fact not only 
evidenced by the extent and volume of snow and ice but also by the 
great areas over which climates still prevail which are not very far 
removed from the glacial and which could become glacial with a slight 
decrease in average temperature. 

The formation of snow and ice fields which last for long periods 
represents storage on the earth of water evaporated into the atmos- 
phere and later precipitated as snow. The principal evaporating basin 
is the ocean, though of course a certain amount goes from the waters 
of the lands. As the ice grew during the glacial stages, the 
volume of the ocean gradually shrank. Sea level was slowly lowered 
and the land covered by shallow depths of ocean water emerged. It is 
believed that the maximum fall of the oceans when the ice reached 
its greatest extent and thickness was between 300 and 400 feet, whereas 
at the culmination of the last glacial stage it amounted to 250 or 300 
feet. This caused a small in the size of continents and islands 
and the joining of some large and many small islands to the continents 
or to each other. For example, the water between Alaska and Siberia 
is so shallow that the above-mentioned lowering of the ocean united 
the two areas. The area of California increased somewhat as the ocean 
went down, but the continental shelf off the California coast is narrow 
in most places, hence the increase was not of much moment. The depres- 
sion now occupied by San Francisco Bay had a very different appear- 
ance during the last glacial stage at because the depth of water 
in the Golden Gate is about 381 feet and of the bay is quite 
shallow. Therefore when the ocean reached its lowest stand, the bay 
had largely disappeared and was not restored to material size until 
sea level had risen appreciably thus bringing the development of the 
present bay down to the last few thou-sand years. 

Four times during the Glacial epoch ocean level fell and four times 
it rose, though there appears to have been a slight drop in very recent 
time occasioned by a moderate chilling of earth climate and some 
increase of ice. A large volume of water is still locked up in the Green- 

land and Antarctic sheets and a much smaller amount in other ice 
masses. Calculations indicate that, if this ice disappeared, sea level 
would rise between 50 and 100 feet around the earth. This would 
submerge many exceedingly low areas along continental and island 
shores and low islands; also, drowning of the land would isolate 
certain higher areas as islands. 

The profound climatic changes which brought on and did away with 
the glacial stages naturally were felt far beyond the limits to which 
the ice expanded. In both hemispheres, though more conspicuously in 
the northern because of its greater land acreage, the belt of eastward 
moving storms with its cloudiness and precipitation shifted equator- 
ward as the glacial stages advanced toward their climax, spreading 
over many regions which are semi-desert or desert today and bringing 
greater precipitation over both lowlands and highlands. In more 
northerly and southerly lowlands and particularly in adjacent moun- 
tains, both rainfall and winter snow increa.sed. Streams multiplied or 
grew in volume ; lakes without outlets expanded, some developing 
outlets ; and great numbers of new lakes appeared. The changes were 
more notable in the poleward and higher parts of the regions arid 

It is clear that each maximum spread of greater humidity over the 
present dry regions coincided with the culmination of each glacial 
stage. This climate prevailed about 55,000 years ago. when the fourth 
glaciation reached its height. The present aridity has evolved prin- 
cipally during the last 25,000 years when the ice recession has been 
most rapid. Today desert climate prevails over about 35 percent of 
the land above sea level and vast areas are semi-desert. 

The very dry parts of western United States present a splendid 
record of this climatic change. Professor Flint of Yale University has 
shown that there are 128 closed basins in this region where evidence 
of 98 former lakes or expansions of existing lakes has been obtained. 
Only 8 basins have not yielded positive evidence of former lakes and 
20 have been insufficiently studied to show whether lakes were present 
or not. The 98 basins contained 71 lakes, as some flooded more than 
one basin. 

Mono Lake, at the eastern base of the central Sierra N'evaila. was 
much larger and during the third glacial stage attained a depth of 
nearly 900 feet. Owens Lake at the .south end of Owens Valley in- 
creased notably in size. In the Mojave Desert section of the Basin- 
Ranges province there is record of many former lakes, some of goodly 
dimension. Panamint Valley held a large one, and another, more than 
90 miles long and some 6tX) feet deep, lay in Death Valley, now one of 
the most arid regions of the world. The evidence of these former lakes 
and expanded existing lakes includes wave-cut cliffs and a.ssociated 
wave-cut terraces standing at various elevations along the sides of 



[Bull. 158 ]Y« 

-^jL-2'* --^^^^^-^^s^e.-'-.- ■• - ■ - -ii«/>9' - •'JEf'a^'St^^- -^ '>&^^S^•^^■- 

Fio. 12. Vosemite roKinn fnun .Mt, Spem-.r. K>„lul,„u Has... in foreground. Mt. Huxley to left. Mt. Goddard to right. Photo bv Oeorge J. You„g. 




the mountains apainst which waves pounded, topether with beach sedi- 
ments and other deposits laid down in quiet waters. 

It is true that, since the culmination of the last glacial stage about 
55.000 years ago. the climate of the earth has become warmer and 
drier and the ice blanket has notably diminished ; but there have been 
fluctuations both in the climite and in the stand of the ice during 
even this interval. Neither the advance to the climax of a glacial stage 
nor its recession has continued unbroken. In very recent times there is 
abundant evidence of one of these fluctuations, for the greatest warmth 
and dryness of the fourth glacial stage was reached between 6.000 and 
4,000 years ago. Since then, also with minor fluctuations, earth climate 
has become somewhat cooler and moister. Even as late as 500 B.C.. 
the general climate was warmer than today. This warm, relatively 
dry episode which began to wane so late in human history is termed 
the Climatic Optimum. 

The proof of the climatic change just referred to is both geologic 
and biologic. For example, in the Sierra Nevada it has been shown 
that the regional snow line was considerably higher than today, the 
average summer temperature also was higher, and the summer season 
was somewhat longer. This means that none of the small valley-head 
or cirtiue glaciers are remnants of former valley glaciers, as had 
long been believed, but are infants conceived during the cooler interval 
which started about 4.000 years ago. To judge from the speed with 
which these glaciers are now wasting, it seems impossible that they 
could have survived the greater warmth of the Climatic Optimum. The 
extreme youth of these glaciers also is shown by the freshness of the 
debris composing their moraines and by the fact that the moraines in 
some instances contain cores of glacier ice. Moraines of older glaciers, 
those born during the fourth glacial stage, are somewhat weathered 
and contain no ice cores. 

Certain lakes, like Owens in California, do not contain as much salt 
as they should if they were residues of larger lakes evaporated to their 
present size. Therefore it is believed that these lakes disappeared 
during the climatic optimum and have been recreated in the last 4.000 
years. It is possible that most or all existing lakes in western North 
America may have had similar histories, but this has yet to be proved. 

Since the present Sierra Nevada began to rise only a little before 
the beginning of the Glacial epoch, it soon felt the effect of the increas- 
ing cold. The climate became more wintrj" and the higher parts of the 
range were blanketed by snow and ice which did not disappear during 
the slightly warmer months. As the glacial stages advanced, the snow- 
ice piles became thicker' and thicker until they generated glaciers, most 
of which moved down canyons already scored deep into the rocks by 
rivers. However, on the western side, the rolling uplands between the 
canyons provided sites for the generation of small and not particularly 

thick ice caps, most of which sent tongues into the canyons, adding to 
the glaciers already descending from cirques being eroded into the 
canyon heads. On the ea.stern side, where the snowfall was less, the 
valley glaciers were thinner and shorter and there was no room for 
ice-cap formation. However, tongues from certain caps on the western 
side found their way into the eastern canyons, as for example, in the 
Tioga Pass section above Mono Lake. 

In the relatively low, northern section of the Sierra Nevada, where 
the high peaks do not much exceed 6,000 and 7.000 feet above sea level, 
only cirque or valley-head glaciers and short valley glaciers were 
present. Since this portion of the range has received little geological 
study, ice effects are not well known. South of the Kern River where 
again the peaks are lower as they approach the terminus of the range 
at Tehachapi Pass, there was little or no glacial ice. The long section 
between these two parts, however, is quite different. 

Around Donner Pass, which is crossed by Highway 40. glaciers of 
the last stage measured 10 to 15 miles in length and apparently joined 
to form an ice field approximately 250 square miles in area. Donner 
Pass was overwhelmed by ice during each of the four stages, long 
tongues projecting both to the east and west. 

Toward the southern end of Lake Tahoe. where the peaks on the 
western side are 9.000 to 10.000 feet high, the later glaciers on the west 
side of the main crest were at least 20 miles long, the earlier ones 
shorter, measuring only 5 to 10 miles. So bulky was the ice mass that 
part of it was forced across the divide and this together with short 
valley glaciers developing on the eastern side descended into Lake 
Tahoe. Between Lake Tahoe and Yosemite National Park, the crests 
rise from 11.000 to 13.000 feet above sea level. So much snow fell in 
this section that, on the rolling uplands — remnants of the elevated 
ancient landscapes — a domed ice cap formed which ran along the trend 
of the range for about 80 miles and had a width of about 40 miles. 
Above this considerable ice mass only the highest peaks projected as 
lonely nunataks. From the cap, tongues flowed into canyons already 
eroded by rivers, and its volume was great enough to force some ice 
upward through low passes onto the eastern side of the Sierra Nevada. 
The largest glacier invaded Tuolumne Canyon and in the earlier 
glacier stages had a length of about 60 miles. The lesser ice of the last 
stage did not descend the canyon more than 46 miles. 

The Yosemite glaciers were the shortest of the tongues in the section 
under discussion, for most of the ice formed in a relatively small basin 
and there was only a modest contribution from the ice cap. 

Another considerable ice mass about 50 miles long and 30 miles 
wide developed in the broad basin of the upper San Joaquin River 
and there were adjacent masses in the basins of Dinkey Creek and the 
North Fork of the Kings River. The main body was not a cap like 



[Bull. 158 

Fig. 13. Ciriiuf ;;l;icior on Mt. M:u-Iure in the Sierra Nevada. Photo by 
O. K. Qilhert, courtesy V. S. Geological Survey. 

that in the Yosemite-Tahoe region, for it appears to have been formed 
by the union of several valley glaciers too thick to be contained in the 
canj-ons where they originated. In the last glacial stage, there was not 
enough ice to create such a field and the glaciers were held within 
tlieir canyons. The principal ice tongues in this area followed the 
Middle and South Porks of the San Joaquin River, starting from 
Evolution Basin and joining into a short trunk stream at Balloon Dome. 

In the Kings River drainage area, the canyons were so deep that 
the ice was held in them. The Middle and South Fork glaciers were 
the chief ones but the supply was insu(ficient to cause them to join so 
they remained separate streams. 

In Kaweah Basin, each tributary canyon harbored a vigorous 
glacier 5 to 7 miles long. The main mass of ice in this region, however, 
lay in a section extending from Tokopah Valley to the head of the 
Marble Pork of Kaweah River. 

The southernmost of the Sierran valley glaciers lay in the Kern 
River canyon. During the earlier glacial stages, the ice overflowed the 
canyon onto the surrounding bench lands which are parts of old valleys 
generated before the last elevation of the range. The glaciers of the 
last stage seem to have been confined to the Kern Canyon and its 
tributaries. The earlier ice was about 32 miles long, extending down 
to the vicinity of Hoekett Peak ; the last ice was about 7 miles shorter. 

Ilockett Peak appears to mark the southern limit of glaciation in the 
Sierra Nevada. 

Today, there are about 60 tiny glaciers in the high Sierra, the best 
known being two on Mount Lyell, a third on Mount McClure, and a 
I'ciurtli, the Palisade glacier farther south at the head of Big Pine 
Creek. All are true glaciers, though they are now shrinking, and, 
because of their small size, they move very slowl}^ They arc not rem- 
nants of earlier valley glaciers belonging to the culmination of the 
fourth glacial stage, but have been created during the slight upswing 
of the cold, known as the "little ice age." Prom evidence at hand, it 
appears that these miniature glaciers began to evolve about 4,000 
\oars ago. Jlost of them lie in high peak cirques * facing north and 
northeast though some are on the north and northeast slopes of nar- 
row, comb ridges. In all cases, they are located where abundant snow 
is drifted by the wind and where they are protected from the sun by 
the great rock walls above. 

The upper part of the Merced River canyon in the Yosemite region 
was invaded by ice at least three times during the Glacial epoch. The 
Yosemite glaciers were formed by two principal tributaries, one 
descending Little Merced canyon south of Half Dome and Liberty 
Cap while the other followed Tenaya Canyon on the north side. The 
two streams joined about where Camp Curry and the Awahnee Hotel 
are now located and proceeded down the main canyon. The first two 
glaciers were much thicker and longer than the third ; little evidence 
remains of the initial stream but the second and third left a fine record. 
The Merced River canyon prior to the appearance of the ice probably 
was 1,200 to 1,500 feet deep and possessed the usual V-shaped contour 
of such gorges. When the glaciers reached their maximum, they filled 
the canyon which was being appreciably deepened and widened by 

' A cirque is a steep-walled, round-bottomed amphitheater evolved by glaciation of 
the head of a mountain canyon. 

Fio. 14. Dotted line shows probable cross section of Yosemite Valley before 
Klaciation. Solid line shows the present cross-section and figures indicate amount of 
widening and deepening by the glaciers. After F. E. Matthes, V. S. Oeol. Survey 
Prof. Paper 160, p. S5. 




their erosive action. The modi6eations cannot be correctly appor- 
tioned to the various ice tongues, but in total the canyon was deepened 
about 1,500 feet at its head where it was widened 1,800 feet on the 
north side and 1,700 feet on the south side. Excavation decreased in 
amount downstream. Glacier Point along the rim at the upper end of 
Yosemite Valley was covered by about 700 feet of ice, but Sentinel 
Dome which stands a mile back from the rim, the upper 700 feet of 
Half Dome, the top of El Capitan, and Eagle Peak, highest of the 
Three Brothers, were not overwhelmed. The lower limit of the ice 
projected perhaps 5 miles below El Portal where the typical glacial 
U-shaped canyon begins ; the lower few miles of the glaciers were thin 
and did not erode that part of the canyon to any extent. 

The last glacier was much thinner, measuring about 2,700 feet at 
the head of Yosemite Valley, instead of more than 4,000 feet as did 
the third glacier, and extended only a short distance below the great, 
bold promontory, El Capitan. This tongue of the fourth stage left a 
terminal and a number of recessional moraines as its fluctuated after 
its maximum advance. Recessional moraines are ridges of debris 
comparable with a terminal moraine and roughly paralleling it. They 
are developed by temporary advances of the ice after recession from 
the maximum development has begun. One of the recessional moraines 
lies a little below El Capitan and now appears as a high embankment 
well covered with trees and shrubs. It contains great numbers of 
granitoid boulders embedded in finer debris. As the glacier receded 

Elev above 
sea level 

Fio. li>. Section across Tenaya and Little Yosemite Canyons showing highest levels reached by glaciers in the second (Glacier Point) and third (Wisconsin) stages. 

After F. E. ilattkei. V. S. Geol. Surrey Prof. Paper 160. p. 8S. 

Ml. L>«ll^ 

Kio. 16. 

Longitudinal profile of the two last glaciers that occupied Yosemite Valley and its tributaries during the glacial epoch. The lower solid line shows the last 
upper solid line indicates the much thicker and longer tongue of the ice of the third glacial stage. .l//er F. E. ilatlket, V. S. Geol. Surrey Prof. Paper 160, p. 





[Bull. 158 

Fio. 17. Bird's-eye view of the Yosemite Valley as it probably was immediately 
after the ice age. The valley had been broadened and deepened to essentially its 
present proportions. The deepening accomplished by the ice ranged from 600 feet 
at the lower end to 1,500 feet at the upper end. A lake 5J miles long occupied a basin 
gouged into the rock floor of the valley and dammed in addition by a glacial moraine. 
After F. E. Matthes, V. 8. Oeol. Survey Prof. Paper 160, p. i9. 

up the valley from this moraine, a short, wide lake formed between 
the ice front and the rock barrier. With continued withdrawal of the 
ice, the lake grew until it extended to the upper end of Yosemite 
Valley, then attaining a length of about 6 miles. Because of the greater 
amount of glacial erosion toward the head of the valley than farther 
down, a basin had been formed sloping in that direction from the 
lower section where erosion had been much less vigorous. The moraine 
therefore merely increased the depth of the basin and the lake was 
much deeper at its upper end than its lower end, measuring perhaps 
300 feet. When the lake reached its greatest size, upper Yosemite 
Valley must have been a glorious sight with the great, deep blue body 

of water fringed by gray walls rising nearly vertically above it. But 
Lake Yosemite did not last long in terms of geological time for into it 
quantities of sediment were poured by streams coming from the 
waning ice; thus the basin was filled rather rapidly. At the upper 
end the delta, as such deposits are known, finally rose slightly above 
average water level, forming at first a small delta plain. This advanced 
down the lake until it reached the crest of the dam, driving out the 
last of the water. The tributary streams formed the post-glacial 
Merced River which developed a serpentine path over the even surface 
of the delta plain until it came to the morainal dam down which it 
plunged into the unfilled, lower section of the canyon. Thus, though 
the lower part of Yosemite Valley as far as El Portal is a characteristic, 
trough-shaped, glacial canyon, the upper part has a flat floor, covered 
with trees and other vegetation. Since the disappearance of the lake, 
the Merced River for some unknown reason seems to have rather 
suddenly developed a shallow breach in the dam. cut a trench about 
15 feet deep into the sediments, and then proceeded to widen its valley 
into a flat floor over which the river lazily meanders. 

Little Yosemite Valley, which was evacuated by the ice considerably 
later than the main Yosemite, had a roek-basin lake about 2J miles 
long and a mile wide. Since the basin does not appear to have been 
more than 50 feet deep, it was filled even before Lake Yosemite. 

Mirror Lake in the mouth of Tenaya Canyon is not a glacial product 
but was impounded by landslides, particularly from a place on the 
west wall of the canyon behind the Washington Column. This lake 
is being rapidly filled with sediment, though steps are now being 
taken to prevent its destruction. 

In no other Sierran canyon is there a lake history which matches 
that of upper Yosemite Valley. Small lakes, chiefly of the rock-basin 
type, are present and many have been filled, or nearly so, developing 
little meadows, but no large lake is known to have existed. 

The deepening and widening of the valley together with the trim- 
ming off' of spur ends between tributary gorges have given the bold, 
barren sides which stand so prominently above the valley floor. The 
excavation was greatly facilitated or hindered by the abundance or 
scarcity of joints, for where they were closely spaced removal by 
quarrying was easy, but where widely separated it was relatively 
ineffective and wear was accomplished by abrasion. The widest part 
of the valley, the upper half, therefore lies in closely jointed rock, but 
the lower part and the tributary gorges are in rock jointed less prom- 
inently. In the main valley, the widening decreases from about 1,800 
feet on either side to a minimum of 500 feet on either side not far 
below El Capitan. 

Ascent of the Yosemite, Tenaya, and Upper Merced canyons is 
accomplished by a series of steps, another characteristic of glaciated 




Fic. 18. Present configuration uf Yosemiie Valley. Merced River now meanders through the filled-in bed of Lake Yosemite. Photo courtesy U. S. Armjf Air Corps. 



(Bull. 158 

Fig. 19. Yosemite Valley from Wawonu road. To the left is El Ciipitiui. I.i the richt Cathedral Rock and Bridalveil Fall. 
Photo by J. T. Boysen, courtesy V. S. Qeologicat Survey. 




J M 

flu. -0. View up LiltJe Yoseniite \'al]ey. Photo court* a u I'. S. Army Air Curpa. 


[Bull. 158 






[Bull. 158 

i :'^> 

Fio. 23. I'pper drop of Yosemite Falls (about 1,430 
feetl. as seen from Merced River. Nortnan E. A. Hinds, 
OEOMORPHOLOOY (copi/right 19^3 by Prentice-Hall, 
Inc., AVtr York). Reproduced by permission of the publisher. 

canyons. The risers of the steps have been evolved in rock cut both by 
vertical and nearly horizontal joints where quarrying was easy ; the 
edges of the steps and the treads between them are in relatively 
unbroken rock, which resisted this type of erosion. Each tread is 
essentially a basip, and the edges are barriers of virtually unquarry- 
able rock, smoothed on the upstream side by abrasion and steepened 
on the downstream side by removal where more abundant jointing 
begins. Excavation took place most actively at the head of each tread 
for there the ice exerted its greatest force because of its plunge down- 
ward from the step above. 

Thus is explained the replacement of the steeply rising irregular 
preglacial canyon bottom by a nearly level, basined rock floor, and 
also why the excavation by the ice was nearly three times as great at 
the upper end of Yosemite Valley as at the lower. The ice entered the 

valley not only by the great stairway from whose steps Vernal and 
Nevada Falls now plunge, and from Tenaya Canyon, but also by a 
gigantic cataract from a cap of moderate size on the rolling upland 
at the base of Half Dome. The deep, walled-in headfe of Little Yosemite 
and Tenaya canyons also were excavated by similar ice cataracts 
coming from the sheet ice on the upland. 

Joints determined the level of each step in the valley. The high 
stand of the Little Yosemite above the main eanj'on resulted from the 
height of a very massive body of granite that forms the upper step of 
the great stairway in that canyon. The absence of such a step at the 
mouth of Tenaya canyon is explained by the presence there of jointed 
rock which greatly aided glacial excavation. 

Evolution of the minor features of the walls of Yosemite Valley also 
have been controlled by the jointing which has played a most signifi- 
cant part in the weathering that has taken place. 

Vertical master joints have controlled the position and profile of 
most of the great cliflf faces, including the sheer precipices over w-hich 
the falls plunge. The smooth, sheer front of Sentinel Rock is bounded 
by such a joint. Where there is little fracturing, the relief features are 
massive, as for example the great promontory. El Capitan, which 
rises so boldly for 3,000 feet above the valley floor. Cathedral Rocks 

Fio. 24. 

Glacial striae in rocks along middle fork of Kincs River south of 
Grouse Meadow. Photo by George J . Young. 




Flc. '2o. Royiil Arches, Washingtuu Culumn (nui 

•me (upper center). Photo by F. E. .\tatthe$, courtesy I 



[Bull. 158 

also have been sculptured into some of the most masshe rock in 
the entire valley. In contrast are frail Cathedral Spires where the 
jointing is more closely spaced ; elsewhere manj' recesses which have 
been excavated along narrow, abundantly broken zones. The Royal 
Arches have been etched into a complexly jointed slanting cliff face 
about 1,500 feet high. Along highly inclined and curved joints, frost 
wedging has pried loose blocks bounded by these fractures. The Wash- 
ington Column standing just east of the arches has been carved out 
of a less broken mass or rock. 

Adding great beauty to Yosemite landscape when water is abundant 
are the many falls which plunge from hanging valleys standing at 
various elevations above the valley floor. Most waterfalls are broken 
in their descent by projecting ledges and should properly be called 
cascades; it is primarily in glaciated valleys that this less common, 
high, free-leaping type of waterfall is present, though some are formed 
in other environments. The streams responsible for the Yosemite Falls 
are small and consequently thej' appear as veils or ribbons of water 
rather than as massive cataracts, except for those of the Merced which 
are somewhat heavier. During the dry season the streams decrease in 
volume, the falls become largely misty clouds, and some disappear. 

Bridal Veil is one of the most perfect examples, emerging from 
the edge of a V-shaped guleh and plunging over a precipice 620 feet 
high. In the spring and early summer when the snow is melting the 
torrent is of considerable size, but during the rest of the year it is 
filmy and veil-like. Directly opposite on the other side of the valley, 
Ribbon Falls drop 1,612 feet from the edge of the upland ; it is the 
highest of all, but does not make a free descent throughout for it is 
held in a narrow, sheer-walled recess in the side of the valley. Even 

Fig. 2G. Diasrara showing how, by progressive exfoliation, the 
original angularities of a rock mass are replaced bv smooth curves. 
After F. E. Malthes. V. S. Geo!. Survej/ Prof. Paper ISO. p. 115. 

though they are produced by a stream of modest size, Yosemite Falls 
are the supreme spectacle of the valley. They are in three sections, 
the upper dropping over a cliff 1,4.30 feet high and being one of the 
highest if not the highest free-leaping fall in the world, though it does 
not clear quite this entire distance in a free plunge. Then the water 
scatters over several acres, collecting into sheets and rivulets that 
converge toward a half-bowl of polished granite from which the re- 
made stream races through a narrow winding gorge. After this tor- 
tuous descent of 815 feet, the water again plunges over a 320-foot cliff 
to the floor of the valley. 

In the short stretch of the Merced Canyon that connects the Little 
Yosemite with the main valley, there is an abundance of falling water, 
for the river descends 2,000 feet in a mile and a half. In the upper part 
the stream drops over the risers of the giant stairway producing Vernal 
and Nevada Falls, the former 317 and the latter 594 feet high, and 
farther down races in a series of raging cascades and rapids. 

A rival of Yoi?emite Falls is the Tueeulala in Ilctch lletchy Valley 
which has a total drop of about 1,000 feet, but a free leap of only 
about 600 feet. 

Morainal deposits include the terminal and recessional barriers 
which impounded the lake that lay so lately in the upper part of 
Yosemite Valley, and side moraines along the valley walls which 
have been added to by boulder fall and avalanches from the precipitous 
cliffs after the ice went away. 

One of the features characteristic of a glaciated region is polished, 
scratched or striated, and grooved bedrock, a product of the abrasive 
action of the moving ice. Particularly in resistant rock like granite, 
the polish is often remarkable. The scratches apparently are made by 
sand dragged along by the ice ; the grooves, which may reach a yard or 
more in depth, are formed by resistant boulders grinding into the rock. 
Such features can be produced in other wa.vs, but, where present over 
considerable areas and associated with other features of glaciation, 
can be interpreted only as the product of ice action. 

The famous domes of the Yosemite upland have been evolved from 
giant, joint-bounded columns of granite bj' long-continued exfoliation. 
This breaking off of shells of rock along more or less concentric frac- 
tures apparently has been caused by expansion of the rock as the load 
upon it has been relieved by erosion. Some of these domes in the 
Yosemite region were ice covered, others were not. The breaking off 
of shells of rock has also been aided by the prying action which results 
when water freezes in the joints. The Half Dome has an exceptional 
form because its steep northwestern side, a sheer drop of more than 
2,000 feet, has been exposed only recently as the result of glacial modi- 
fications of the canyon below and the exposure of a nearly vertical 




Fig. 27. Northeast side of Half Dome in Yosemite Valley. Frost wedging of 
joint blocks along a system of curved joints has produced shells that are several feet 
thick. Photo by F. C. Catkins, courtesy U. S. Geological Survey. 

system of joints which controls the precipitous face. The form of the 
southern side is eontrolled by concentric curved joints along which 
frost wedging has pried loose shell after shell. 

Tahoe Region 

In the vicinity of Laice Tahoe, the western mountains range from 
8,000 to 10,000 feet in elevation, are broken by deep valleys which 
have been much ice worn and have prominent cirques at their heads. 
In the valleys are many rock basins and the characteristic stairway 
topography already described from the Yosemite section. The moun- 
tains in part are narrow ridges but certain areas like the Tallac-Dick's 
Peak range liave broad, flat summits. The higher parts were not cov- 
ered by ice and consequently have topography characteristic of vig- 
orous mechanical weathering, gravity transfer, and snow avalanehing 
above the limit to which the ice extended. In the mountain canyons 
there are few morainal deposits. Ice-abraded surfaces prevail, but 
such features as grooving, striation. and polishing have been exten- 
sively destroyed by rock weathering which lias followed disappearance 
of the glaciers. In some places there is considerable burial by talus. 

When the ice reached its maximum thickness, it covered all but the 
higliest ridges and tlat summits, moving principally from a large area 
of accumulation in Desolation Valley. Tongues traveled north, east, 
and south. Other glaciers came from cirque heads of valleys tributary 
to the main ones. While the main movement was down the valleys, 
several of the lower divides between them also were covered. This 

Fig. 2.S. Rock basin lakes and Fallen Leaf Lake. Lake Tahoe in the distance 
occupies the southern part of a long, narrow fault basin. Photo courtesy Southern 
Pacific Railroad. 

zone of vigorous glaciation possesses the wildest, most spectactilar 
scenery to be found about Lake Tahoe. 

Toward the lake is a zone of morainal ridges and irregular hiUs in 
which there are a number of lakes behind morainal barriers. The 
landscape is far different from that of the mountainous section pre- 
senting little that is startling but much that is beautiful. In this zone 
are Fallen Leaf ami Cascade Lakes and Emerald Bay ; the upper end of 
each is a basin scoured out of the bedrock, the lower end of each is made 



[Bull, 158 

Vi... :;'.>, Kiiio I 


,:ike ( fi>resrou 
tern part t>f \v 

ml) lies in a glacially eroded rook basin. Fallen Leaf Lake (left niiilille Kriiuiidl i» iMipounded liy a terminal moraine, while Lake Tahoe. the 
hich shows beyond Fallen Leaf Lake, is contained in the lowest part of the Tahoe fault basin. Pholo hn V. S. Army Air Corpi. 




by a combination of lateral and terminal moraines. At the southern 
end of the lake plain extending south from Lake Tahoe there is an 
extensive area of morainal hills and ridges left by a combined piedmont 
glacial mass formed by tongues moving northward in the upper 
Truckee Valley and eastward through Echo Lakes basin. 

At the southern end of the Tahoe fault basin is a series of flat plains 
standing at three levels. The most extensive of the three was formed 
by outwash left by subglacial streams coming from glaciers which lay 
to the west and south. About 20 feet below this outwash plain is a 
lower, much less extensive series of terraces eroded by the L^pper 
Truckee River since the ice receded. About 20 feet above the outwash 
deposit is the third section of the plain ; its origin is uncertain but it 
very possibly represents deposits of the larger Lake Tahoe before its 
waters developed the outlet eastward by erosion of Truckee River 

In the heart of the western mountain areas is Desolation Valley, 
or, as it is called on certain maps. Devil 's Basin. On its southwestern 
border rise the bold slopes of a range dominated by Pyramid Peak 
(elevation 10,200 feet) which constitutes a barrier between the basin 
and a group of westward oriented valleys. The Cracked Crags separate 
Desolation Valley from Glen Alpine and Echo Lakes valleys, and north- 
directed spurs from the Pyramid Peak Range and Jack's Peak unite 
at Mosquito Pass and form a divide beyond which is Rockbound Basin. 
Southward a |rroup of low hills partly isolate Desolation Valley from 
the steep gorge down which its drainage flows to the South Fork of 
the American River. 

During at least some of the glacial stages, ice so filled Desolation 
Valley that it overflowed northward into Rockbound Valley, eastward 
into Glen Alpine and Echo Lakes valleys, and southward into the can- 
yon of the South Fork of the American River. The relatively low 
elevation of the divides crossed by the glaciers in part has resulted 
from the hea\y wear by the advancing ice. 

Largest and most complex of the valleys in this region and perhaps 
the most attractive scenically is Glen Alpine. In it lies Heather, Susie, 
Half Moon, and Grass lakes, which occupy rock basins, and Gilmore 
Lake which is held in by a morainal dam. There are prominent cirques, 
particularly at the head of Half Moon Valley, and the canyon sides 
exhibit evidence of vigorous glacial erosion. The rounded rock knobs 
called roches moutonnees are fairly abundant in the valley bottoms. 

Echo Lakes valley is similar to, but is not branched like Glen Alpine. 
Lower Echo Lake is unique in that it occupies a rock basin on the 
southeastern rim of which is a low morainal ridge. The remainder of 
the eastern rim is bedrock, from which there is a long, steep, ice-worn 
slope descending to the lake plain. Down this slope Echo Lakes glacier 
must have plunged as a gigantic ice cascade. 

In the northern part of this mountain section the valleys tributary 
to Cascade Lake and Emerald Bay show glacial features similar to 
those in the Desolation area, but they were developed by glaciers which 
grew in the valley heads. 

Rockbound Valley also was deeply eroded by ice flowing in from 
Desolation Basin. 

The longest valley beading in this glaciated mountain region is that 
of the South Fork of the American River. In the upper part are 
abundant morainal deposits and as.sociated marshy flats, doubtless 
fills of small lakes lying between the morainal ridges. This morainal 
cover extends down the .valley about a mile southwest of Phillips, 
beyond which glacially eroded features are prominent as far as Lovers' 
Leap, about 3J miles to the southwest. 

Mount Whitney Region 

The Mount Whitney region of the Sierra Nevada lies a little south 
of the middle of the range and is the highest part of the fault block. 
Mount Whitney, 14,496 feet above sea level, is its culminating summit. 

Normally the higher part of a mountain range of great altitude 
which has been powerfully eroded consists of an alternation of deep, 
narrow canyons separated by high and narrow crested ridges sur- 
mounted by sharp pointed peaks. If such a landscape has been intensely 
glaciated, the boldness and raggedness of the topography is greatly 
increased. Mount Whitney and many other peaks in this and other 
sections of the Sierra Nevada, however, have gently sloping, table-like 
summits which could not have been formed by initial erosion ; rather 
they are gradually being destroyed by weathering and removal of 
debris. Therefore these mountains must belong to an earlier cycle of 
erosion when the landscape looked quite different from that of today. 
Because of the long time which has elapsed since the first building of 
the range, 120 to 130 million years, we see none of the landscape 
developed by the deformation, but we do see relics which have been 
carved from it. The great folded and faulted ridges brought into being 
by the compression of the region are gone, but fortunately in places 
their roots are still preserved showing the structures which were 
evolved. In the southern two-thirds of the range, ero.sion has gone 
deeper into the granitoid batholith which formed in the heart of the 
mountains as they were originally elevated. None the less, there are 
scattered remnants of folded and faulted cover which had projected 
farther than the average into the intrusive mass. After the ancestral 
Sierra Nevada had been eroded for about 60 million years, it had 
been so worn down that there remained only rows of hills probably 
marking the sites of the original deformation ridges ; beyond were 
lowlands sloping gently westward toward the ocean and for an 
unknown distance to the east. Between the ridges, the streams flowed 
mostly in northwesterly and southeasterly directions as they had done 



(Bull. 158 

Mount Whitney. ATorman E. A. Hinds, QEOMORPHOLOQY (copyright 19^3 by Prentice-Hall, Inc., Neu> York). Reproduced by permission of the publisher. 

from the early days of the range, with less important drainage directed 
toward the southwest and northeast. 

Possibly 40 or 50 million years ago began the first of a series of 
uplifts vhich eventually led to the development of the present Sierra 
Nevada. The Sierra and the country east of it seems to have been tilted 
to the southwest so that new master streams flowing in that direction 
were created. However, lesser streams between the ridges were unable 
to change direction and continued in their previous courses parallel 
to the trend of the range. As each uplift occurred all of the streams 

were invigorated and cut young canyons deeper into the rocks of the 
range, the principal ones directed to the southwest, lesser ones to the 
northwest and southeast. 

In the evolution of present Sierran relief the northwesterly-south- 
easterly crests roughly paralleling the principal crest along the eastern 
margin are of prime significance. They are among the oldest features of 
the landscape and are inheritances from the original ridges of the fold- 
fault range. Some of these longitudinal crests have been carved into 
folded and faulted rock, as for example the Ritter Range. The south- 





F:o. 31. 

Sierra Nevada, California. Huge talus cniit-s nn^i talus aprons extend far up the walls of the deeply glaciated canyons. }iorman E. A. Hindi, OEOMQRVUOLOQY 
(copyright 19^3 by I'rentice-Itall, Inc., A'eir York). Reproduced by permission of the publisher. 

eastward-trending upper canj-on of the Middle Fork of the San 
Joaquin River, paralleling the Ritter Range as far south as Pumice 
Flat, has been eroded into the same mass of rock and follows the direc- 
tion of the folds. Le Conte Divide is another example. On the other 
hand, the South Fork of San Joaquin River has cut its northwestward- 
trending canyon in the rock of the batholith. 

Farther south in the headwaters of the Kings River and in Sequoia 
National Park, where the folded structures of the Sierra Nevada bend 
farther south and southeastward, the principal crests and valleys 

follow them but are carved mostly in granitoid rock. The Great 
Western Divide contains folded rocks in the vicinity of Mineral King 
and in the Kaweah group. The upper Kern River canyon is cut entirely 
in the batholithic rock ; Mount Whitney itself is composed of the same 

The crest of which Whitney is a part and for which the name Muir 
has been appropriately suggested, runs south-southeastward for about 
17 miles from Shepherd Pass on the north to Cottonwood Pass on the 
south. It contains seven of eleven peaks in the Sierra Nevada whose 



32. Mt. Whitney and the Sierra crest. A'ormon E. A. Hinds, GEOMORPHOLOOY (copyright 194S by Prenlice-Uall, Inc., 
New York). Reproduced by permission of the pubiisher. 

elevations exceed 14,000 feet — Tyndall, Williamson, Barnard, Rus- 
sell, Whitney, Muir, and Langley — as well as several which are only 
slightly under that elevation. West of this crest is the upper part of 
the Kern River canyon. The river's position may have been determined 
by tlie ridges on either side, or by a fault, which may be of equal 
antiquity and which was easier to erode than the unbroken rock on 
either side. 

There are features on the east side of the Muir crest which suggest 
that another longitudinal valley of great age lay in that direction, a 

valley generated long before the late elevation of the Sierran region 
and the depression of Owens Valley. The crest appears to have been 
more sharply outlined by valley deepening east and west of it during 
the episode of elevation, perhaps 40 or 50 million years ago. Many 
of the peaks in the various crests show a summit platform similar to 
that of Whitney and some of them slope downward on one or more 
sides to what evidently were at one time broad valleys. At this time 
Mount Whitney was a dome-like hill which rose about 1,500 feet 
above the adjacent valley floors. The distance from the sea coast was 







'^'' ■^- 


. ^* 

Kio. Xi. 

Franklin Pass. Mineral Kini^ is to left of tbe ruige along the skyline. 
Photo by OforgeJ. Young. 

Tvi. M. 

Ml. Metjee and Kvtilution Itasin. Debris in center was left \>\ siacier. 
Photo 6y George J. Young. 

less than today, for the oi-ean covered much of the region now occupied 
by the Coast Ranpes and the Great Valley, but the peak must have 
stood at least 50 miles inland. Comparing this with other regions, it 
has been concluded that the elevation at the base of the "Whitney 
Hill" was perhaps 500 feet, so its summit stood approximately 2,000 
feet above sea level. 

The many flat-topped peaks in the high Sierra similar to Whitney 
evidently are of the same origin. Perhaps most striking is Table 
Mountain (13,464 feet) in the Great Western Divide on the opposite 
side of the Kern River Canyon from Mount Wliitney, but there are 
others in the vicinity. These peaks are about 1,000 feet lower than 
Whitney, but they are 10 to 15 miles farther west where the general 
slope of the range carries them to lower elevation. Farther north in 
the range are Darwin, which has two separated platforms standing 
at altitudes of l.'),841 and 1.3.701 feet, respectively; Kuna, Koip, and 
Blacktop in Yosemite National Park which together form a continuous 
platform about 3J miles long and between 12.500 and 13,000 feet in 
elevation. Parker Peak (12,8.50 feet). Mount Gibbs (12,700 feet), and 
Mount Dana (13,050 feet) are other examples. The lower elevation of 

these more northerly peaks is consonant with the slope of the crest of 
the fault block in that direction from the Mount Whitney region. 

Mount Whitney is about 1,000 feet higher than other peaks in the 
immediate vicinity which have rounded or gently sloping summits, 
such as Young, Hitchcock, Lone Pine, and Cirque. Mount Langley 
( 14,042 feet ) also exceeds by a similar amount summits in its neighbor- 
hood. Furthermore the smoothly curving slopes of these lower moun- 
tains descend to levels at about 12,000 feet and seem to have been 
evolved with reference to lower valley floors than either Whitney or 
Langley, whose slopes descend to remnants of a former valley which 
now stand nearly 13,000 feet above sea level. Thus it seems that the 
first elevation of the Sierran region in early Cenozoic time caused 
the streams to carve canyons about 1.000 feet deep on both sides of the 
crest of which Whitney and Langley are a part, and of course, similar 
erosion occurred elsewhere in the range. During the quiet that fol- 
lowed this disturbance the streams passed from youth to maturity, 
widening their valleys by cutting terraces into the bedrock on either 
side of their courses. At the same time the mountain slopes were worn 
back to rather gentle angles. This uplift increased the elevation of 



[Bull. 158 

Fig. 35. Part of Evolution group 







Fio. 36. The Sierra Nevada Id the vicinity I'f Mount Whitney, California. Before the last elevation of the range, the high peaks were low. rounded mountains rising little 
over 2..KW feet above wide valleys, a fine example of which shows in the middle ground of the photograph. The canyon of the Kern River has been eroded as the range has 
risen to its i>resent height. All of the peaks and canyons have been deeply glaciated. A great cirque has been eroded into the eastern side of Mount Whitney, the peak in 
the foreground. .VormOB E. A. Hindi. OEOilORPHOLOGY (copyright 194S 6v Prenlice-IIall, Inc.. Xetc York). Reproduced hn permission of Ihe publisher. 

Mount Whitney to about 4,000 feet, and, because of the valley erosion, 
caused it to stand another 500 to 600 feet higher above its immediate 
base. Also, long spurs were carved on both sides of the crest, which are 
represented by Mount Young (13,493 feet) and Lone Pine Peak 
(12,951 feet). 

West of Cirque Peak and about 1,500 feet below its rounded summit 
is a gently undulating plateau that extends unbroken for 7 miles to 
the canyon of the Kern River. This plateau undoubtedly represents 
part of a broad valley developed by the ancestral Kern River following 
a second uplift ; other remnants are Guyot Flat northwest of Mount 



[Bull. 158 

Trough-like glaciated river canyoDS, cirques, and snow avalanche sculpture in the high Sierra Nevada near Mount Whitney. Norman E. A. Hinds, QEOMOR- 
PHOLOOY (copi/right 194S hy Prentice-Bait, Inc., Neic York). Reproduced by permittion of the publither. 

Guyot and Bighorn Plateau between Wallace Creek and Tyndall Creek. 
Apparently this second deformation, which occurred in late Miocene 
and early Pliocene time, added about 3,000 feet to the elevation of 
Mount Whitney, so that it stood 7,000 feet above sea level. Its height 
above its western base resulting from this further valley cutting was 
about 2,000 feet as compared with the 500 feet of the "Whitney Hill" 
first described. 

About 1,500 feet below the terrace remnants just described lie broad, 
gently sloping rock benches that flank the deep Kern River canyon. One 

of these is the Chagoopa Plateau which rises from an elevation of about 
8,600 feet at the canyon rim to about 10,500 feet at the base of the 
mountains. These benches are clearly remnants of a former broad 
valley of the Kern River eroded after a third period of uplift which 
seems to have added about 2,000 feet to the elevation of the Sierra 
Nevada, thus raising the summit of Mount Whitney to about 9,000 
feet. Probably this was part of the Miocene-Pliocene deformation. 

The present Kern River canyon, like other deep canyons in the 
Sierra Nevada, is the product of vigorous stream erosion accompany- 




ing the elevation of the region which started just before the beginning 
of the Glacial epoch and has continued with notably decreased inten- 
sity until the present. The part of the Kern River canyon in the Mount 
Whitney region is 2,000 to 2,500 feet deep and has been strongly 

The U-shaped form of the upper part of the Kern River canyon is 
the product of glacial modification of a normal V-shaped river canyon. 
There were at least three invasions by the ice and further study may 
reveal a fourth. Tributary to the master gorge are the canyons of 
Wallace, Whitney, Rock, and other creeks. Because of the recency of 
elevation in the Sierran region, these tributaries have eroded gorges 
only about a mile in length, at the mouths of which water plunges 
precipitously into the main canyon. Thus they are hanging valleys 
such as are present in the Yosemite and other sections of the Sierra 
Nevada. The glaciation of the valley of Whitney Creek differs mate- 
rially in its various parts. In the lower section, the ice was never more 
than 600 feet thick and wrought only moderate changes ; but, near the 
base of Mount Whitney, where two tributary glaciers joined, the com- 
bined tongue exceeded 1,000 feet in depth and the glacier remained 
longer than it did far down the valley, altering the original form of 
the river-cut gorge to greater degree. 

On the eastern side of the Muir Crest, vigorous ice attack pro- 
foundly modified the canyon heads by eroding large cirques which 
worked back, destroying pre-glacial slopes and spurs and even carrjang 
away part of the main divide as between Mount Whitney and Whitney 
Pass, where only the western slope now remains. In some places, as 
south of Mount Le Conte, the divide was attacked from both sides, 
and was reduced to a narrow, ragged, comb ridge; in others, as be- 
tween Mounts Whitney and Russell, the growth of opposing cirques 
was so extensive as to leave only a thin rock wall. In a few localities, as 
between Mounts McAdie and Mallory, the divide was destroyed and 
replaced by a saddle. 

Mount Whitney must have been a dome of considerable bulk, even 
if not of great height above its surroundings, or it would have been 
reduced to a thin spire like its neighbor. Mount Russell. Even so, the 
entire eastern half has been cut away by small, but long-lived glaciers 
which lay upon its slopes until comparatively recent times. Destruc- 
tion still goes on vigorously because of frost wedging and the fall of 
multitudes of loosened blocks down the steep slopes. A considerable 
section of the north side of the peak was removed by the glacial 
widening of a canyon between it and Mount RusseU, and on the west, 
the lower pre-glacial slope has been destroyed by the enlargement of 
Whitney Canyon while occupied by ice. The southeast side also lost a 
small slice by the incision of a narrow cleft, the northernmost of a 
similar series that break the crestline at intervals of more than a mile 

to the south of Mount Whitney and through which occasional views 
may be obtained to the eastward from the trail up the mountain. These 
clefts are not glacial features but have resulted from active frost wedg- 
ing aided by snow sliding along vertical zones where the granite 
appears to have been sheared by ancient faulting into thin, rather 
easily removable vertical plates. Only on the southwestern side does 
Whitney retain its original pre-glacial slope which connects it with 
the equally unglaciated slope of the main divide. 

The upper slopes of Mount Whitney and the entire length of the 
Muir Crest show no evidence of glacial attack, in striking contrast with 
the abundant evidence of such action in the upper San Joaquin and 
Tuolumne drainage areas and in the Kaweah, Kings, and Kern basins. 
This probably results from the close proximity of the Muir Crest to 
the southern limit of Sierran glaciation and also to the effect of the 
Great Western Divide upon which the rising air currents delivered 
most of their moisture as they do today, thus keeping a greater share 
from the Muir Crest. Such topographic barriers produce striking cli- 
matic contrasts within short distances. 

Above the level of the ancient glaciers, the sides of Mount Whitney 
are furrowed by parallel or converging snow or avalanche chutes 
developed by powerful erosion as the great snow cascades swept down 
the steep slopes. Some of the chutes are 50 to 100 feet deep, and, 
where close together, are separated by narrow rock ribs which give 
the cliffs a fluted appearance. The bottoms of the chutes have been 
worn smoothly concave by the abrasive action of rock carried along 
by the snow slides. Avalanche chutes are best developed on the west 
side of Mount Whitney, though they also show well on the north side. 
Even more perfect, though not so deep, are those on the north side of 
Mount Hitchcock and in the cirque at the head of Wliitney Canyon. 
The Whitney region is especially rich in this t\-pe of sculpture because 
of rather regular joint and fault structure in the granitoid rock which 
makes for easy erosion. In other parts, where the joints are more 
widely spaced or irregular, the chutes are sparse and not well 

Studies indicate that snow conditions prevailing on the flattish sum- 
mit of Mount Whitney are closely related to evolution of the chutes. 
The avalanches producing them come largely from snow blown to the as great "snow banners" by terrific winds sweeping across the 
top of the mountain. Although most of the snow goes eastward, con- 
siderable amounts are driven in other directions, accumulating as 
massive cornices at the edge of platforms, with the snow now and then 
collapsing to produce the avalanches. 

Today in the winter the flat tops of the Sierran peaks are covered 
only with a thin mantle of snow because of the powerful winds which 
sweep across them ; this condition seems to have prevailed during the 



[Bull. 158 

glacial stages. Therefore these summits have escaped the ice attack 
which has been so effective at lower elevations. Not only this, but there 
also has been little stream erosion to modify thejr contour. Heavy 
showers are rare at such high elevations and snow melts too slowly to 
produce streams of water. In fact, most of the water sinks into the 
rocks where it freezes during both summer and winter, cracking the 
rod; to produce the great multitude of blocks which cover the tops of 
the flat peaks and have fallen down the slopes to form huge talus cones 
and aprons. 

Thus we have in Mount Whitney and most of the other peaks of the 
high Sierra, hills and low mountains belonging to a time when the 
highest stood not more than 2,000 feet above sea level and the Sierra 
Nevada was anything but an imposing region. This perhaps was 60 
million years ago. The changes which have followed have produced the 
remarkable multiple landscape, of which extensive remnants have 
been preserved because the vigorous erosion accompanying the late 
elevation of the range has not had time to destroy them. 

Glacial Lakes 

In the glaciated sections of the Sierra Nevada are hundreds of small, 
very beautiful lakes which add immensely to the glory of a landscape 
undoubtedly almost lakeless prior to invasion by the ice. Although 
there may have been a good many lakes and swamps when the Sierran 
region was worn down to its lowest stand 60 million years ago, it is 
certain that few existed as the mountains rose ; the normal processes 
of mountain erosion are against their formation as the land is too 
much broken up by active streams. A few basins may be evolved by 
faulting, landsliding, or volcanic action but their total is far short of 
the number present in those sections of all mountain ranges remodeled 
by ice. 

The present lakes were produced by the latest glaciers though 
undoubtedly many were formed as the earlier sheets and tongues left 
the range. Perhaps in many cases the thinner and weaker glaciers of 
the last stage merely cleaned out debris-filled basins excavated by the 
earlier, more powerful ice masses, but without doubt they dug addi- 
tional basins. In the high Sierra, where the reservoir ice supplying 
the glaciers evolved in canyon heads and eroded cirques, it etched 
depressions into the bedrock in which lie hundreds of cirque lakes. 
In this part of the range, and also in the lower northern and southern 
sections, cirque lakes are most abundant on northeast slopes where 
the snow was drifted by the prevailing westerly winds and where 
melting was least effective. The peaks above such lakes are typically 
unsymmetrical, being steeply cliffed on the northeast side, where the 
cirques have been incised, and more rounded on the southwest. The 
rounded slopes are remnants of the ancient hills and low mountains 
which had been evolved prior to the late elevation of the region. 

Cirques not occupied by the last ice have been considerably modified 
by erosion, their bottoms filled with great masses of talus, and lakes 
that were present have been converted to meadows. In cirques where 
the last ice grew, the rock is generally so bare as to indicate that the 
glaciers have very recently left. Where several cirques are being 
eroded opposite each other in valleys radiating from a dome-shaped 
peak like most of those in the pre-glacial Sierra Nevada, the cirque 
lakes are separated by high ridges commonlj' having exceedingly 
ragged crests and the peak itself has been reduced to a steeply sloping 
spire. On the other hand, if several pre-glacial valleys headed in a 
group of mountains and converged into a trunk canyon, the cirques 
have a similar converging pattern, the smaller ones hanging above 
the canyon. The cirque lakes of such a group therefore are closely 

In the Sierra Nevada there are many cirque lakes in basins developed 
under one of the two conditions described above. In the higher middle 
section they are present by the hundreds but farther north and south 
where the glaciation was less intense there are not so many. Gold Lake, 
at the head of a tributary of the Middle Pork of the Feather River, 
has a length of about 2 miles and is one of the largest cirque lakes. 
Somewhat farther south below Sierra Buttes near the North Fork of 
the Yuba River and around Fall Creek Mountain near the South Fork 
of the same river, are two groups of lakes. A number of small cirque 
lakes lie at the headwaters of the Kaweah River in Sequoia National 
Forest, and fourteen of them, more or less completely converted to 
marshes, are clustered around the head of the Stanislaus River. 

In some of the U-shaped valleys, basins have been excavated below 
the cirques. The lakes filling them, starting with those in the cirques, 
are connected by a stream flowing in and out and from a distance 
look like beads of turquoise or sapphire on a chain. The basins are in 
places particularly susceptible to erosion where the rock was closely 
jointed, or where it was slightly less resistant than the immediately 
adjacent rock. Such chains of lakes are found in the headwaters of 
Illilouette Creek, 16 miles southeast of Yosemite Valley, between Mam- 
moth Mountain and Mammoth Crest high on the eastern slope of the 
Sierra Nevada 22 miles south of Mono Lake, and farther south in 
the Sixty-Lake basin at the headwaters of the Kings River below 
Mount King. 

Garnet Lake and Thousand Island Lake, which have a roundabout 
drainage to the Middle Fork of the San Joaquin River, stand out 
among cirque lakes because of the many rocky islands rising above 
their surfaces. 

A few lakes like Silver, Loon, and Pleasant in glaciated branches 
of the South Fork of the American River appear to lie in the lowest 
parts of unevenly eroded valley floor. Where the valleys are narrow 
and steep walled, such lakes are long and oval in plan, being larger 




Ki.i. :>.^ ri-..iL,iii,ui ^ii..w uialaDcbe scalpturing on the side of a peak in the Mount Whitney region. Where rock structures are favorable the avalanche chutes are sep- 
arated by narrow, ragged rock ribs like those in the foreground. Mormon B. A. Hindi. GEOMORPHOLOGY (copvrigkt 194S by Prentice-Hall. Inc.. Xew York). Repriy- 
duced 6v permiiMion of the publither. 

than the normal rock-basin lakes ; but if the glacial trough is wider, the 
lakes are broader, irregular in outline, and commonly have rocky islets 
projecting from them. 

In the barren, wind-swept, rolling upland toward the higher part 
of the range, where remnants of the ancient landscape are preserved 
ami where iee caps evolveii, small nx'k-basin lakes, such as in Devil's 
Basin, a wide area at about 8,200 feet at the head of the South Fork 
of the American River, also are present. Humphrey Basin, at about 

11,000 feet at the head of the South Fork of the San Joaquin River, is 
another example. In this area is Desolation Lake, about 1 mile in length. 
Certain lakes lie at or toward the end of the glaciated section of a 
canyon and are partly impounded by a barrier of morainal material. 
The most familiar example is Donner Lake (elevation 6.400 feet) 
about 3 miles long, on Highway 40 on the east side of Donner Pass. 
In the same drainage basin, but less often seen because it lies higher 
in the mountains to the northeast is Independence Lake (elevation 




(Bull. 158 

FlO. 39. 

Donner Lake east of Donner Pass in the Sierra Nevada. Tlie lake has been impounded by a terminal moraine left by a glacier whieh advanced down the valley 
shown in the foreground. In the distance are Tahoe fault basin and Carson Range. Photo courteay U. S. Army A,r Corps. 




7,000 feet), which is 2 miles in length. Well-known Fallen Leaf Lake 
(about 6,400 feet) on the southwest side of Lake Tahoe is about the 
same size as Donner Lake and its barrier is a relatively low moraine 
of the last glacial stage. However, beyond this deposit are huge 
moraines of the preceding stage ; one southeast of Fallen Leaf Lake is 
about 3 miles long and rises abruptly for 900 feet above its surround- 
ings. Cascade Lake, 3 miles northwest of Fallen Leaf and of about 
the same size and altitude, lies behind a compound loop of morainal 
deposits. Twin Lakes, having a combined length of 3 miles, and more 
than 7,000 feet high on a fork of the Walker River 15 miles southwest 
of Mono Lake, also lie behind a moraine and have been separated by 
the growth of delta plain deposits near the middle. 

Many of the Sierran lakes have been filled or nearly filled with sedi- 
ment and now are meadows covered either with small vegetation or 
trees; these meadows are some of the most delightful spots in the 
Sierran canyons. The best known is that in Yosemite Valley. Another 
occupies the lower part of Tenaya Canyon, northern tributarj- of the 
Yosemite, and is the fill of a rock-basin lake. Still a third of larger 
size occupies part of Little Yosemite Canyon. One of the longest filled 
areas is Tuolumne Meadows which apparently represents the filling 
of several closely spaced rock-basin lakes. 

Most of the meadows are larger than the lakes were, for the deposits 
generally have spread in some or all directions beyond the margins 
of the basins. 

Numerous lakes impounded by landslides from steep canyon walls 
are present in the Sierra Nevada. Mirror Lake in Yosemite Valley is 
one of these. Another is Kem Lake in Kern River canyon. 

Artificial Lakes 

Many reservoirs have been established in the Sierra Nevada for 
flood protection, water storage for irrigation and other uses, and power 
generation. Some of the principal examples are Almanor near the 
intersection of Highways 36 and 89 at the north end of the Sierra 
Nevada, a group in the Mokelumne basin which supplies water for 
cities on the east side of San Francisco Bay and another, principally 
Hetch Hetchy Reservoir, which is the principal source of San Fran- 
cisco's water supply. Still other artificial lakes of considerable size are 
the Pardee Reservoir near Jackson, the Calaveras Reservoir near San 
Andreas. Near the mouth of the canyon of the San Joaquin River is 
the Friant Dam which impounds Millerton Lake ; this is the second 
most important element in the great Central Valley Project which is 
so vital to the Sacramento and San Joaquin Valleys. The principal 
unit in this project is the huge Shasta Dam in the Klamath Mountains 
of California. Water is to be exported to various parts of the eastern 
side iif the southern San Joaquin Valley from Millerton Lake to bolster 
the underground and surface waters which have been severely tapped 


I, 4 * ..,*f^ 

-V,; . . -«r ■ '-'-- •~^-^~ 


Fio. 40. Heather I^ke. Alia Peak region. Sierra Nevada. The smoothed rock 
surface has beeo produced by glacial abrasion. Photo courtftp L'. ^'. Sotu^nol Park 



I Bull. 158 


Fig. 41. Four stages in the filling of Kern Lake in Kern Canyon, Tulare County, liy deposition from the inHowing stream. The lake apparently was formed in ISfi" by 
a landslide from the west wall of the canyon which for a time dammed the river. If depcsition continues as is probable, a forest-covered lake plain or meadow will be 
formed. A. 1010; B. 1918; C, 1928. Photos by T. A. Church. 




by frrowing population, agriculture, and industrj*. Many of these 
reservoirs have become pleasure resorts to which hundreds of people 
go for outings of various types. 


Along part of the Kern and Little Kern canyons are the Palisades, 
part of a lava field that shows at least four distinct flows, each of which 
possesses rather crudely developed columnar jointing perpendicular to 
the flow surface. This jointing developed as the lava cooled and con- 
tracted. In other places in the field there are more flows, but thin, 
weathered zones between them makes separation difiicult as the lavas 
are similar in composition. The total thickness of the lava in remnants 
that are left exceeds 400 feet ; how much has been removed by erosion 
cannot be determined. 

In the Toowa Valley below Toowa Range — a high valley drained 
to the west by a stream kno\vn variously as Godel, Trout, Volcano, 
or Little Whitney creek, and to the east by the South Fork of the 
Middle Kern River — there is another volcanic field which covers an 
area about a half mile wide and 4 to 7 miles long. This field contains 
flows and cinder cones. Cinder cones are small volcanoes, generally 
less than 1,000 feet high, composed entirely of lava fragments. Most 
of them are built during brief eruptive cycles lasting a few days, 
weeks, or months. 

Toowa Valley is broad and open and stands at an elevation of about 
8,600 feet. The cones rise from 400 to 600 feet above the veneer of 
flows which covers the bedrock. The latest activity blocked drainage, 
as two prominent cones lie along the axis of the valley — South Fork 
Cone where Golden Trout Creek enters Toowa Valley, and Ground- 
hog Cone 2 J miles farther east. Two other volcanic centers are in the 
vaUey, one at the head of Little Whitney Meadow and one at the Tun- 
nel, north of South Fork Cone. The activity has been so recent that 
soil is scanty and therefore vegetation is sparse. Several stages in 
the total eruptive cycle are recorded. It is evident that these eruptions 
occurred long after the major faults outlining the eastern base of the 
Sierra Nevada had been evolved. 

Earlier basalt apparently of pre-glacial age poured from vents in 
the canyon of the North Fork of Oak Creek and spread over an 
alluvial cone formed by the stream issuing from its mouth. Later this 
lava was partly eroded and covered by debris of the first glacial stage. 
Basalt flows, probably of the same age, form a number of isolated 
patches on the south side of Bishop Creek which issues from the 
Sierra Nevada. 

Another considerable volcanic area is located in the headwaters of 
the Middle Fork of the San Joaquin River to the east of the towering 
range which has Mount Ritter, Banner Peak, and The Minarets as its 
principal peaks. The summit of the range is somewhat over 13,000 

feet above sea level; Mount Ritter rises abruptly more than a mile 
above an area of much gentler relief which finally ascends to the lower 
main eastern divide of the Sierra Nevada, a crest much less imposing 
than those to the north and south. The rolling area between the two 
mountainous barriers probably was part of one of the flat valleys 
belonging to a landscape evolved prior to the last elevation of the 
Sierra Nevada. The section described has been extensively covered 
by pumice and lava which is believed to be at least 2,000 feet thick 
in places. The frothy pumice fragments were exploded from a series 
of cones at least 30 in number lying mostly east of the Sierra Nevada 
and extending from Mammoth Mountain to Mono Lake, and includ- 
ing the Mono volcanic range. Most of the pumice came down around 
the volcanic pipes forming the volcanoes but finer debris was carried 
far by the wind and is found sprinkling a considerable part of this 
section of the range. Mammoth Pass and the divide for several miles 
north are most heavily mantled, and Pumice Flat, as the name indi- 
cates, has a goodly cover. Even at Reds Meadow and farther south 
along the Middle Fork of the San Joaquin River, there is a thin 
veneer of pumice. 

From the alignment of the cones, it is evident that they are located 
along some of the faults evolved during the great landscape changes 
in the eastern part of the Sierra Nevada. Certain of these fractures 
apparently penetrate into the range for some distance as is indicated 
by the fact that Mammoth Mountain, a greatly worn old volcano, the 
Little Red Cones on the east side of the Middle Fork, and Pumice 
Butte north of Fish Creek stand in line with them. The well-known 
hot spring near Reds Meadow, though somewhat to the west of the 
line of cones, probably rises along a branch of this fracture sj^stem. 

Volcanic eruptions occurred along these faults at different times. 
Mammoth Mountain, a modest eminence which belies its name, was 
built prior to the beginning of the Glacial epoch and therefore is more 
than a million years old. So much time has elapsed since activity 
ceased at this vent that the original form of the cone has been destroyed 
and there remains only a shapeless mass of volcanic debris. The pumice 
outbursts are the latest chapter in the recurrent eruptions along the 
faults, having begun late in the fourth glacial stage and continuing 
until quite recent time, though not within the historic period. 

During the third interglacial stage, more than 100,000 years ago, a 
fissure opened in ^lammoth Pass and from it spilled a flood of basaltic 
lava most of which streamed into the canyon of the San Joaquin's 
Middle Fork, spreading out as a tongue from the head of Pumice Flat 
beyond Rainbow Falls : the flow was at least 6 miles long and is believed 
to have ranged from 100 to 700 feet in thickness. As the rock cooled 
after consolidation from the molten liquid, it contracted and joints 
formed which broke it into rather easily removable columns. 



[Bull. 158 



1 „. 4-. i;,.Mer„ l.u^,. „f U... Sur.u NVwida. ..,.|-.,ral, ,1 l.> u fault .l.prefision from one of the westernmost of tbe fault blocks of the Basin Ranges Province. 



^r"!!^.^*^. u..AS^^W*ti 

North of Keno. Nevada. Fhoto courtety Wfalern Pacific Railroad. 



Fio. 43. Feather River Canjon near Rock Dam. Photo cotirtety Western Pacific Railroad. 



[Bull. 158 

When the last glacier descended the Middle Pork canyon, the lava 
flow formed an obstruction in its path ; but the ice was about 1,000 
feet thick and therefore overrode the barrier. The prominent jointing 
made possible easy quarrying by the glacier which was present long 
enough to remove most of the lava and re-excavate the canyon down 
to the granitoid rock beneath. Only the most resistant parts of the 
flow escaped destruction. The largest remnant is a hump in the middle 
of the canyon which is about 300 yards long and 200 feet high. Because 
of the roscinblanee of its tall, straight columns to stacked posts, it has 
been called the Devil's Postpile, and a National Monument has been 
created to protect it. 

The columns forming the steep western front of the Postpile are 
high, straight, and very clearly outlined, but those at the southern 
end are even more remarkable for their curvature and radial arrange- 
ment with respect to a center at the top of the pile. On this upper 
surface may be seen the five- or six-sided ends of the columns, in places 
still possessing the polish and striations given to them by the over- 
riding glacier. 


Atwood, W. W., Jr., Crater Lake and Yosemite through the ages : National 
Geographic Magazine, vol. 71, pp. 326-343, 1937. 

Beatty, M. E.. A brief story of the geology of Yosemite Valley ; Nature Notes, 
Special Number, National Park Service, 1943. 

Blackwelder. Eliot, Pleistocene glaciation in the Sierra Nevada and Basin 
Ranges : Geol. Soc. America Bull., vol. 42, pp. 865-891, 1937. 

Blackwelder, Eliot, Supplementary notes on Pleistocene glaciation in the Great 
Basin : Wash. Acad. Sci. Jour., vol. 24, pp. 217-222, 1934. 

Davis, W. M., The lakes of California : California Jour. Mines and Geology, 
vol. 29. pp. 175-236, 1933. 

Flint, R. F., Glacial geology and the Pleistocene epoch, John Wiley and Sons, 
Inc.. 1947. 

Hills, T. M.. Gliicintion of the upper Kern and its tributaries: Sierra Club Bull., 
vol. 12, pp. 17-1!), 1928. 

Jones, W. I).. Giaoial land forms in the Sierra Nevada south of Lake Tahoe : 
Univ. California Pub. Geog.. vol. 3, pp. 137-157, 1929. 

Kesseli. J. E., Studies in the Pleistocene glaciation of the Sierra Nevada : Univ. 
California Pub. Geog., vol. 6, pp. 315-361, 1941. 

Knopf, A., and Kirk, E., A geologic reconnaissance of the Inyo Range and the 
eastern slope of the southern Sierra Nevada, California : U. S. Geol. Survey, Prof. 
Paper 110, 1918. 

Lawson, A. C, The geomorphology of the upper Kern Basin, California : Univ. 
California Dept. Geology Bull., vol. 3, pp. 291-376, 1904. 

Lawson, A. C, The geomorph(dogic features of the Middle Kern : Univ. California 
Dept. Geology Bull., vol. 4, pp. 397-409, 1906. 

Louderback, G. D., Lake Tafaoe, California-Nevada : Jour. Geography, vol. 9, 
pp. 277-279, 1911. 

Jjouderback. G. D., Morphologic features of Basin Range displacements in the 
Great Basin: Univ. California Dept. Geol. Sci. Bull., vol. 16, pp. 1-42. 1926. 

Matthes, F. E., Kings River and Yosemite Valley: Sierra Club Bull., vol. 12, 

pp. 224-2.36, 1926. 

Matthes, F. E, 
Sierra Club Bull. 

Matthe.s, F. E. 
Paper 160, 1930. 

Matthes, F. E. 

Devil's Postpile in the Sierra Nevada and its strange setting : 

vol. 15, pp. 1-8, 1930. 

Geologic history of Yosemite Valley : U. S. Geol. Survey Prof. 

Geography and guidebook of the Sierra Nevada : 16th Internat. 
Geol. Cong., Guidebook 10, pp. 26-40, 1933. 

Mnttbi-s. F. E., The Op..loKic hisforv of Mt. Whitney : Sierra Club Bull., vol. 22. 
pp. 1-18. 1937. 

Matthes, F. E., Avalanche sculpture in the Sierra Nevada of California : Internat. 
Assoc. Hydrology Bull. 23, pp. 631-637. 1938. 

Matthes, F. E., The incomparable valley, Univ. California Press, 160 pp., 1950. 

Matthes, F. E., Sequoia National Park, Univ. California Press, 136 pp., 19,50. 

Miller. W. J., Geologic sections across the southern Sierra Nevada of California : 
Univ. California Dept. Geol. Sci. Bull., vol. 20, pp. 331-360, 1931. 

Putnam. W. C. Quaternary geology of the June Lake district, California : Geol. 
Soc. America Bull., vol. 60. pp. 1281-1302, 1949. 

Reid, J. A., The geomorphogeny of the Sierra Nevada northeast of Lake Tahoe : 
Univ. California Dept. Geol. Sci. Bull., vol. 6, pp. 89-161, 1911. 

Webb, R. W., Kern Canyon fault, south Sierra Nevada : Jour. Geology, vol. 44, 
pp. 631-638, 1936. 

Webb, R. W., Geomorphology of the middle Kern River basin, southern Sierra 
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Margining much of the eastern boundary of California and includ- 
ing a considerable part of the southeastern section of the state is a 
section of the Basin-Ranges province which consists of north-trending 
ranges separated either by completely enclosed basins or by troughs 
open at one or both ends. 

In northeastern California, the forces evohnng this province 
invaded the Modoc section of the great Columbia lava plateau ; the 
Warner Mountains, which mark the western boundary of the province 
in this section are composed entirely of lava. On its western side the 
Basin-Ranges province abuts against the eastern base of the Sierra 
Xevjula : its southern boundary adjoins the Mojave Desert province. 

The portion of the Basin-Ranges province lying in California in- 
cludes part of the belt folded into mountains by the deformation in 
Jurassic time. During the Cretaceous and earlier part of the Tertiary, 
this region, like the Sierra Nevada, underwent long erosion together 
with certain re-elevations, the details of which are little known at 
present. In the later part of the Tertiary period, the region was sub- 
jected to further deformation, mostly large- and small-scale fault- 
ing, though some local folding took place. Along the faults certain 
blocks were elevated to form a new generation of ranges, while inter- 
vening blocks were depressed in similar fashion, developing basins or 
troughs called graben. The result has been the evolution of many 
discontinuous mountainous areas, most of which are relatively small 
and not particularly high. Some, like the White-Inyo and Panamint 
ranges, are much more bulkj- and tower thousands of feet above the 
bordering lowlands. None of the blocks approaches the Sierra Nevada 
in size or maximum elevation. 

Throughout the Basin-Ranges province, elevation and depression 
have been mostly rotational, giving iUied range and graben blocks, 
though some horsts (vertically elevated blocks) are present. However, 
many ranges have been so deeply eroded that their original form 
cannot be determined. 

Most of the basin ranges have been examined in reconnaissance 
fashion, but verj* few have been studied in detail; more is known 
about certain of the grabens. So actually there is relatively little 
information about this vast region, though its general history can 
be partly outlined. 

In general the province is arid, much of it highly so ; the drjiiess 
increases from north to south and is more intense in lower than in 
higher basins. Precipitation in Death Valley, one of the lowest spots, 
averages about 1.4 inches annually. Independence, in southern Owens 
Valley (3,957 feet) receives 4.83 inches. Bishop at the north end 
(4,450 feet), 6.05 inches. Over the ranges, particularly the higher 

ones, more moisture falls, but there is very little record of this. There 
is snow on the higher ranges during the colder months, heavy falls on 
the more northerly and higher ranges, lighter on the lower and more 
southerly ranges. There also is considerable snow over the northern 
and higher basins, little or none over those at lower elevation and 
farther south. The rains are principally summer thunder storms 
which concentrate over the mountains. 

Many of the basins contain lakes ; some are permanent, others con- 
tain water only part of the year or during intervals separated by more 
than a year. Most of the lakes are saline or alkaline. On the east and 
west sides of the Warner Mountains in northeastern California are 
Goose and Middle Lakes. Mono Lake is at the eastern base of the Sierra 
Nevada below Tioga Pass. Owens Lake in the southeastern part of the 
valley of that name formerly was fairly large, but the Los Angeles 
aqueduct which takes water from the head of Owens River has mate- 
rially reduced its size and will do the same to Mono Lake. Honey Lake, 
about 70 miles northeast of Reno, Nevada, and just inside the Cali- 
fornia border, is dry during the summer. 

The Truckee River, flowing from the north end of Lake Tahoe, 
empties into Pyramid Lake about 35 miles northeast of Reno. Farther 
south, some streams flowing down the eastern side of the Sierra Nevada 
empty into Mono Lake. The Owens River, also supplied from the 
Sierra Nevada, ends in Owens Lake. 

Springs emerge at many places in the mountains and basins. Most 
of the ones in the mountains provide good water, as do some in the 
basins ; but many of the latter have taken up such quantities of salts 
as their waters have traveled underground that they are anything but 
potable. Since good springs are of such importance to desert travelers, 
signs noting their location or the distance to them have been posted at 
many places, and the government has published various bulletins 
giving much information about them. 

Travel off the main highways in the Basin-Ranges province should 
not be undertaken without first making careful inquiries about water- 
ing places and condition of roads; also proper equipment for a region 
in general quite hostile, but wonderfully interesting, is essential. 

The concept that the ranges and basins of this geomorphic province 
originated from dislocations along faults was first advanced in 1873 
by G. K. Gilbert of the United States Geological Survey. Another 
member of the same survey, J. E. Spurr, later attempted to account 
for them as eroded folded mountains since he was unable to find posi- 
tive evidence of faulting along the margins of many of the ranges. 
It is recognized that the elevation and depression of the blocks started 
at different times in different parts of the province and that it con- 




[Bull. 158 

tinued longer in some areas than in others. Ranges whose elevation 
started earlier and ended sooner naturally have changed more than 
those elevated in very late time or those in vehich elevation still con- 
tinues. Along the older ranges evidence of fault control has been 
largely or wholly wiped out, but in the more recent ones it is clearly 
defined. Between the two extremes are intermediate stages which can 
be recognized when the province is studied as a whole. Therefore the 
absence of clear-cut fault-controlled land forms by no means proves 
that such were not once present. 

The size of the fault blocks varies greatly ; low ones that make dis- 
tinct ridges are only a few miles long and a mile or so wide. The length 
of .the largest blocks is several tens of miles or even more than 100 
miles, and their highest peaks rise several thousand feet above the 
basins. The width of these major ranges may be only a few miles or 
may reach a few tens of miles. 

In the Basin-Ranges province, the fault basins and troughs be- 
tween the ranges, such as Owens Valley, Panamint Valley, and Death 
Valley, are narrow compared with the width of the ranges. The 
boundary fault systems outlining one or both sides of a range can be 
recognized easily in most places where elevation still goes on or has 
recently ceased. In older ranges, the fracture systems have been buried 
by debris from the ranges, which is piled along their bases as alluvial 
fans and aprons. These deposits come from streams swollen by flood 
water, carrj-ing coarse sediment down the canyons through which 
they flow, and depositing it quickly when their velocity is checked as 
the water emerges onto the low land at the base of a range. Where 
several fans unite into a single mass, the deposit is called an alluvial 

Along some ranges like the White-Inyo on the east side of Owens 
Valley, the west side of the Panamint Range on the eastern side of the 
valley of that name, and the Black Range at the southern end of Death 
Valley, the fans are small and discontinuous, indicating that vigorous 
recent uplift has interfered with the accumulation of debris at the 
canyon mouths. Elsewhere the fans have joined to form alluvial aprons 
which border more or less the entire mountain fronts. Small knobs or 
ridges of lower ends of divides between canyons may project through 
the mantle of unconsolidated debris. The heads of fans forming the 
great aprons may extend far back into the canyons, in some places to 
the divides which separate them from those on the other side of the 
range. Alluvial aprons may eventually join in the middle part of 
fault troughs or basins with valley-like depressions between them 
down which flash floods from torrential rains occasionally flow. 

One of the best known and most spectacular sections of the Basin- 
Ranges province in California is that included between the eastern 
base of the Sierra Nevada and the ranges on the eastern side of Death 

Valley, 250 miles away. In this region there are three depressed fault 
blocks, Owens Valley, Panamint Valley, and Death Valley, which are 
separated by tilted fault-block ranges. The White-Inyo, Coso, and 
Argus ranges lie between Owens and Panamint valleys ; Panamint 
and Chance mountains separate Panamint Valley from Death 
Valley ; and on the east side of Death Valley are the Grapevine, 
Funeral, and Black Ranges. 

The region exhibits great differences of relief: the elevated blocks 
have peaks ranging from 8,000 to more than 14.000 feet above sea 
level, but part of Death Valley is more than 270 feet lower than the 
level of the ocean. The mountains are newly elevated and therefore 
rugged ; the valleys, on the other hand, have rather even floors. 

Owens Valley is a long basin whose floor is between 2 and 8 miles 
wide; the distance between the crests of the bordering Sierra Nevada 
and White-Inyo Mountains ranges from 15 miles between Bishop and 
Bigpine to 40 miles at the north end and 25 miles at Owens Lake near 
the south end. The floor of the graben slopes gently from an elevation 
of about 3,600 feet at Owens Lake to about 8,000 feet at the northern 
extremity of the valley. South of Owens Lake the land rises to a broad, 
low divide at an elevation of 3,670 feet, which separates Owens Valley 
from Rose Valley to the south. 

The Poverty. Tungsten, and Alabama Hills are isolated low emi- 
nences standing above the floor of the valley, but are quite incon- 
spicuous because of the enormous height and bulk of the great 
bordering ranges. The hills very likely are small, fault-bounded blocks 
though they may possibly be bedrock remnants left by erosion. South- 
west of Bigpine there is a well-preserved volcanic field comprised of 
explosion cones and lava flows, consisting predominantly of basaltic 
material, although slightly older rhyolitic rocks, including glassy 
rocks of various types, are present. Crater Mountain, the highest point 
in the field, is a cone with crater in the top which rises about 2,000 feet 
above the floor of Owens Valley. 

All evidence points to the subsidence of the Owens Valley block 
along a series of parallel boundary faults, one at the base of the Sierra 
Nevada and the other at the base of the Inyo- White Mountains. The 
graben bedrock in turn is broken by minor faults some paralleling and 
some lying transverse to the boundary faults. The subsidence of Owens 
Valley has not been uniform. Partial rotation has occurred and un- 
doubtedly the lesser blocks have moved within the main one. For 
example the basin holding Owens Lake seems to have been evolved by 
this uneven sinking and partial rotation of one of the blocks com- 
posing the graben. 

The rocks composing the Alabama Hills are Triassic or Jurassic 
volcanics which are intruded by granitoid rock unquestionably of the 
same age as that of the batholithic complex in the Sierra Nevada — 




Fig. 44. 

View of Owens Valley and the southern end of the Inyo- White Mountains from the Sierra Nevada near Mount Whitney. The low Alabama Hills in the middle 
ground show remnants of the ancient landscape found in the upper part of the Sierra Nevada around Mount Whitney. 

late Jurassic or early Cretaceous. The oldest rocks in the hills are 
therefore less than 200 million years old. The topography of the Ala- 
bama Hills contrasts strongly with that of the nearby Sierran or Inyo- 
White Mountains fronts, but it is similar to that of the upland around 
Mount Whitney, where there are well-preserved remnants of land- 
scape far more ancient than that of the great scarps marking the 
boundaries of the ranges. It is probable that the Alabama Hills are a 

fragment of this old landscape separated both from the Sierran 
upland and from the bedrock under Owens Valley by the great dis- 
locations which have occurred 

At the base of the Sierra Nevada, there is an alluvial apron com- 
posed of debris brought from the canyons by the mountain streams. 
The individual fans and the apron as a whole have a considerable 
slope, 10 to 15 degrees. Because of the steepness of this slope sediment 



[Bull. 158 I 1' 

Flu. 4."!. The great battered fault .scarp of the Sierra Nevada rises about 11,000 feet above the Hour of Owens Valley in the vicinity of Lone Tine (foreground). The 
houndary fault system lies immediately at the base of the range. The Alabama Hills are in the middle ground. At the base of the range is an alluvial apron. .Yorman E. A. 
Hinds, OEOMORPIIOLOOY (copyright WiS hy Prentice-Hall, Inc., New York). Reproduced hy permission of the puhHshcr. 

which the streams carry, especially during time of flood, when the most 
active addition to the fans occurs, is coarse ; where the slope flattens 
abruptly, mostly fine fragments are carried. On the eastern side of the 
valley, the fans along the White-Inyo Range are isolated from each 
other and are comparatively small. 

Very recent, low fault scarps are present in Owens Valley indi- 
cating movement either along the Sierran boundary fault system or 

along faults roughly parallel to it. Near Lone Pine several small scarps 
cut late stream deposits and were evolved by dislocations at the time 
of the very severe earthquake in 1872 which resulted in much loss of 
life and damage in the town. Because the scarps are in unconsolidated 
debris, they have been considerably eroded ; in height they range 
from a few feet to about 25 feet. Recent scarps may be seen west of 
Bigpine also, one at least being the product of the 1872 disturbance. 



40. Alluvial apron composed of large and small fans on the eastern side of the Sierra Nevada in arid Owens Valley, yorman E. A. Hindi, OEOilORPIIOLOOY 
(copyright I9^S by Prentice-Uall, Inc., New York). Reproduced by permiaaion of the publisher. 

There are many others on the west side of Owens Valley, most of them 
formed prior to 1872. Like those near Lone Pine, most of these declivi- 
ties face eastward, but some are directed toward the Sierra Nevada. 
Horizontal as well as vertical movements are recorded. The total evi- 
dence shows that many recent minor dislocations have occurred along 
a series of roughly parallel faults through a zone 7 or 8 miles wide. 

On the eastern side of the valley, recent scarps are not common ; 
one, several feet high developed in 1872, is visible just north of Swan- 
sea where it traverses an ancient beach of Owens Lake. 

These recent movements are considered evidence of continuation 
of the settling of the sunken blocks, for similar features have not been 
recorded within the main mass of the Sierra Nevada. 



[Bull. i:)S 


FlQ. 47. Red Mountain, an explosion or cinder cone erupted through a granite hill along a fault parallel to the main boundary fault of the Sierra Nevada. The cone is about 

(iOO feet high. Hound about are numerous flows of basalt. This volcanic field lies in Owens Valley. 

Between Bigpine and Independence near the eastern base of the 
Sierra Nevada there is a volcanic field comprised of a considerable 
number of cinder cones and associated lava flows. Some of the cones 
are on faults along which there was movement as late as 1872. Crater 
Mountain, highest of the group, stands about 2,000 feet above the 
floor of Owens Valley, but this considerable elevation results prin- 
cipally from the fact that the explosions burst through a granite hill 

rising nearly 1,400 feet above the valley, hence the cone itself is not 
particularly imposing. 

Most of the cones are on the alluvial apron projecting into Owens 
Valley from the base of the Sierra Nevada, but some lie along the 
lower bedrock slope of the range. The most intense volcanic activity 
occurred between Taboose and Sawmill Creeks where large flows of 
basalt spread far over the valley floor. The flows are extremely rough, 




the surfaces being wild jumbles of clinkery blocks. The lower ends 
of the flows have been partly covered by later alluvium, but because 
of inequalities in their surfaces basaltic eminences project through 
the deposits. 

The most perfectly formed cone is Red Mountain which rises about 
600 feet above the alluvial apron. An extensive basalt flow poured 
from the vent, but the crater rim extends unbroken over the head of 
the flow indicating that the last phase of activity at this center was 
explosive. The cone is built largely of reddish fragments of lava, hence 
its name; most of the debris is angular and individual chunks reach 
an average maximum diameter of about 6 inches, but some bombs 
which were erupted measured at least 4 feet across. Red Mountain has 
suffered some erosion and also burial of part of its lower slopes by 
alluvium, but at first glance it looks as though it were exceedingly 

A large but rather imperfectly formed cone stands on the upper 
end of the alluvial apron between Division and Sawmill Creeks ; scat- 
tered over its top are many large granite boulders evidently derived 
from debris of the apron as the eruptions blasted through it. 

At an elevation of about 7,000 feet on Sawmill Creek explosive 
eruptions occurred and basaltic lava flowed from the vent to the 
mouth of the canyon. 

Considerable basalt is present near the base of the Inyo Mountains 
near Aberdeen on the east side of Owens VaUey. Explosions also took 
place forming a number of imperfect cinder cones, closing the volcanic 
cycle — one that was probably contemporaneous with that on the west 
side of the vaUey. 

Red Mountain, previously referred to, stands at the south end of 
a clearly defined scarp in the alluWum developed at the time of the 
1872 earthquake. A short distance to the north along the same scarp 
there is a minor quantity of exploded debris which did not form a 
complete cone. Still farther north on the projection of the same frac- 
ture is Crater Mountain. Thus three centers of eruption are located 
along this fault, which evidently is still active. 

A large cinder cone west of Fish Springs School was broken by a 
recent fault along which the displacement amounted to about 50 feet ; 
before it occurred the lower slope of the volcano had been partially 
buried by alluvium. 

On the eastern side of most of Owens Valley is a massive block 110 
miles long, with one or two of its highest peaks closely approaching 
the maximum elevations in the Sierra Nevada. White Mountain Peak 
stands 14,242 feet above sea level. The range is a continuous mass 
though there is a depression in the central part culminating in West- 
gaard Pass (elevation 7,276 feet) which lies east of Bigpine. It is 
generally known as the White Mountains, though the southern end 

may still be referred to as the Inyo Mountains. Although there is no 
real demarcation between the two parts, in consideration of local 
preference, the term White-Inyo is used in this description. 

On the north, the White-Inyo Mountains terminate quite abruptly 
at Mount Montgomery ; at the southern end there is a broad depres- 
sion separating them from the Coso Mountains which border the 
southern part of Owens Valley on the eastern side. The south end of 
the White-Inyo block therefore is much less clearly defined than the 
northern. Although the average elevation of the range crest is high, 
more than 10,000 feet, it is considerably less than that of the corres- 
ponding part of the Sierra Nevada on the west side of Owens Valley, 
hence it is somewhat dwarfed by its greater neighbor. 


Fig. 48. The Inyo Mountains are a tilted fault block in the Basin-Ranges 
Province. Rocks in the In.vo Mountains have been intensely folded and are broken 
by great faults, as shown on the cross-section. A large mass of intrusive granite 
shows to the west of Saline Valley. After Knopf and Kirk. 

The west side of the White-Inyo range slopes abruptly to the floor 
of Owens Valley and is only little less spectacular than the east Sierran 
front. The western base against Owens Valley is sharply defined, but 
its eastern margin is much less clear. The northern part of the eastern 
side is marked by the edge of Fish Lake Valley. Between this graben 
and Saline Valley farther south, there is an irregular mountainous 
area not clearly separated from the Inyo Range on the west and the 
mountains to the east. Saline Valley is an elliptical depression whose 
floor is about 2,500 feet lower than that of Owens Valley. The eastern 
face of the Inyo Mountains fronting on this vaUey is quite as abrupt 
and majestic as the eastern side of the Sierra Nevada. 

The White-Inyo Range is a gigantic fault block, but the evidence 
of the dislocations producing it is most clearly shown at the two 
extremities. At the northern end, the inter-canyon spurs projecting 
into Owens Valley are terminated by remarkably large, clearly defined 
triangular facets whose sharp edges and geometric perfection make 
them extraordinarih- fine illustrations of this important feature of 
recently uplifted fault blocks. At the southern end, which is almost 
completely covered by a thick mass of basaltic lava flows overlying 
an exceedingly even elevated erosion surface, actual dislocations of the 
flows are visible. Between the two ends of the range the evidence is 
less conspicuous, probably because the dislocation has been distributed 
along parallel fractures and this has prevented the development of 
prominent triangular facets. Such movements as have occurred in the 



[Bull. IJ" 



* ' '•%. 





\% ^^t:. 


^ ■ ^^"^^ 

Fio. 49. The Whitc-Inyo Mountains on tl ast snli i.l ( iwins Valley are a fault-block rani,-' n-ni. riMi ^Tiiiiller than the Sierra Nevada. Evidence of faulting is prom- 
inent alonK the western front of the range. Owens Lake lying in the lowest part of the fault basin between tlie two ranges shows in the foreground. A'ormiin K. A. Ilinda, 
QEOMORPHOLOOY (copyright 191ii by Prenticellali, Inc., New York). Reproduced by permission of the puilisher. 




middle section appear to have taken place along faults which parallel 
the boundary fault for a distance and then run into the body of 
the range. 

Other evidence of the fault block origin of the White-Inyo Moun- 
tains is the straightness of the western front and its independence of 
the bedrock, for the front transgresses the trend of the rock layers 
as is commonly the case in fault block ranges. The eastern front does 
not provide so straight a base as the western side. However, the topog- 
raphy cif the eastern front in many places shows extensive faulting, 
especially in the great escarpment margining Saline Valley where verj- 
prominent triangular facets are present. Further evidence in the 
same place is the badly crushed rock along this escarpment which 
could only have been produced during dislocation along a major 
fault system. 

The slopes of the west side of the Argus Range, and the east and 
west sides of the Coso, Panamint, and Black Ranges are aU exceed- 
ingly steep, not greatly battered fault scarps. The west sides of the 
Coso, Argus, and Panamint Ranges also include minor scarps known 
to have been developed by step-faulting, for in many places traces 
of these lesser faults can be observed, as well as displacements along 
them. Highway 190 crosses both the Coso and Panamint Ranges on 
its way to Death Valley. 

Perhaps the most conspicuous fault zone bounds the east side of 
Panamint Valley and marks the base of the Panamint Range, for the 
dislocation here has been very great. There are evidences of recent 
movement, particularly south of Wildrose Canyon where the range 
front is extremely high and abrupt and the alluvial fans at the mouths 
of the canyons are feebly developed. For this reason the lowest part 
of Panamint Valley is near the base of the range rather than near the 
center of the valley as is normally the case. However, because the 
volume of debris in the present fans is only a small proportion of the 
total removed from the Panamint Range in the erosion of the canyons 
on its western side, Panamint Valley must have sunk as the range was 
elevated and older fans have been buried by those growing from the 
eastern side of the Argus Range on the opposite side of Panamint 
Valley. Even some of the new fans along the Panamint Range have 
been broken by recent faulting and parts of them elevated. In some 
places, the bedrock scarp, which rises to a height of 2,000 and 3,000 
feet, slopes as much as 35 degrees ; apparently it is the continuous 
footwall of the fault so recently exposed by dislocations. The rock in 
which the facets are cut is greatly crushed, sheared, and discolored, 
additional evidence of the presence of the surface of the fault. 

One of the most striking bits of evidence favoring the recency of 
the faulting along the west side of the Panamint Range is a large north- 
trending graben in the alluvium just south of Wildrose Canyon. This 

depression is more than 3 miles long, nearly a mile wide, and 400 feet 
deep in its deepest part. 

Between the Coso and Argus Ranges is a hiUy area of low relief 
which is a somewhat deformed and eroded portion of an old landscape 
found in the higher parts of the ranges. This section includes Coso 
Valley and the hills immediately to the east, the Darwin Hills, and 
also Darwin Wash. Lower Darwin Wash, east of the Darwin Hills, 
is an alluviated area in which white lake beds indicate the presence of 
a former water body. Headward erosion of Darwin Canyon, a narrow 
gorge which empties into Panamint Valley, has recently drained the 
lake ; as a result the base of erosion for most of the intermittent streams 
draining Darwin Hills and the west slope of the Argus Range has 
been lowered about 2,000 feet, causing considerable dissection of the 
lake beds and the alluvium in Darwin Wash. 

Remnants of the ancient erosion surface are found elsewhere in the 
mountain ranges, and are being progressively cut to pieces by head- 
ward erosion of canyons which have been cut during the late uplift 
of the fault blocks. At one time this surface appears to have been verj- 
widespread over the region and probably was continuous with rem- 
nants found in the Sierra Nevada. In the western part of the section 
under present discussion, thin flows of basalt spread across the ero- 
sional plain completely burj-ing much of it, but, in places, hills several 
hundred feet high rose above the general level and were partially or 
completely surrounded but not covered by the flows. The age of this 
erosion surface which shows in the Sierra Nevada, the Coso, the Argrus, 
and Panamint Ranges at least, is of interest and some information 
is given by geological features in the Coso Range and in the Mojave 
Desert farther south which indicates that the surface had been evolved 
by the late part of the Pliocene or the very early Pleistocene epoch. 
Remnants of a similar surface have been reported from ranges in 
southwestern Nevada and possibly from the San Bernardino Moun- 
tains of southern California. If all are part of a once continuous land- 
scape, a large area had been reduced to most modest relief when the 
late faulting occurred. 

Death Valley, one of California's most interesting and spectacular 
scenic areas, is a completely enclosed graben about 130 miles long and 
from 6 to 14 miles wide. On the western side. Panamint Mountains rise 
to a highest elevation of more than 11,000 feet : the Last Chance Range 
to the north is somewhat lower. Along the eastern margin, three ranges, 
the Grapevine at the north, the Funeral, and the Black at the south 
complete the enclosure. Each of these is distinctly lower than the 

Death Valley basin and the bordering ranges owe their origin to 
such profound fracturing as has been described in areas farther west. 
The deepest part of Death Valley, lying between the Panamint and 


[Bull. 158 

Black Mountains, has been lowered below sea level, though the region 
as we see it today has not been invaded by the ocean. However, in the 
past, before development of the present relief, the sea invaded this 
part of California several times, as is proved by the wealth of marine 
fossils contained in many rock layers exposed in the ranges. 


Fig. TiO. The low cliff in the alluvium at the base of the Panamiut Range in 
Death Valley is a fault scarp formed by recent movement along one of the fractures 
close to the base of the range. Photo courtesy National Park Service. 

The faulting, which started in the late part of the Pliocene epoch 
and is still going on, is extremely complex. Its effects show best along 
the eastern face of the Black Range where the most recent and most 
active movements have occurred. The lower slope of this range is 
extremely steep ; although it has suffered some erosion, it is one of the 
best preserved fault scarps in the United States. The road along the 
east side of Death Valley from Furnace Creek south runs close to the 
scarp and affords easy access. For 15 miles below Furnace Creek, the 
boundary fault system cuts across Tertiary rocks, but, farther south, 
there are precipitous slopes in ancient, resistant formations which 
roughly outline the surface of the fault. Three miles north of Bad- 
water, the deepest point in the valley (270 feet below sea level), a fault 
between the Tertiary and the very old rocks is clearly exposed for 
many thousands of feet where it extends upward into the range, and 
the fault surface is continuous with the vallej^vard slope of the 
ancient rock farther to the south. 

Because of the height of the ranges around Death Valley and their 
ciiiiseiniently steep slopes, a host of val!p_vs has been eroded into them 
and the streams have carried great quantities of debris into the basin 
forming alluvial fans and aprons. Along the Black Range, the fans 
are small and discontinuous and much of the lower part of the range 
front is abnormally steep, both part of the evidence that this block 
has been recently elevated to a considerable extent or that tlir valley 
has sunk. Elsewhere the fans have united to form aprons having mod- 
erately steep slopes from the toe of the deposit to its upper end which 
maj- be miles up the canyons. This is notably true along the west front 
of the Panamint Range where the fan heads extend far back into the 
mountains. The steep slopes of the fans and the coarse debris compos- 
ing them testifies to their speedy formation. In places the fans are 
broken by low scarps, indicating the presence of active faults beneath 
them. A very good example may be seen about a mile south of Furnace 
Creek Inn where a scarp lies just east of the hi^'liway and oxteiuis 
parallel to it for some distance ; another is at the base of the Panamint 

The floor of a considerable portion of southern Death Valley is 
made of rock salt formed by the evaporation of a large lake. As shown 
previously, during the climaxes of the glacial stages, more snow fell 
on the California mountains and in most places over the lowlands more 
rain than does today. At various places around Death Valley, there 
are wave-cut terraces and deposits as much as 600 feet above the valley 
floor. These terraces, although faintly outlined, can be distinguished, 

Fig. 51. Salt left by evaporation of lake in Death Valley is bcinc ciissolvrd by 
water falling on the valley floor and by water mipratinc downward from the adja- 
cent ranges. The water is an exceedingly bitter brine. Photo by Willard. 




Fig. 52. Sketch of Death Valley from the western side. Death Valley is a long narrow fault basin, part of which has sunk below sea level as the adjacent ranges 
have risen. At the base of the Panamint Range, on skyline, is a great alluvial apron formed from debris which streams have brought out of the canyons. The rough land 
in the foreground is weathered salt left when the large lake that formerly filled the basin evaporated. Photo courtesy R. N. Wheeler. 

as for example at Mormon Point and on Shore Line Butte, which is a 
hill of black basaltic lava rising above the valley floor, a mile north- 
west of Ashford Mill. This ancient lake has been given the name of 
Manly, for one of the early explorers in this region. 

Evidences of other lakes which occupied the valley at earlier times 
has been gained from borings into the sediments. A well 1,000 feet 
deep along the road across the Devil's Golf Course, passed through 
alternate beds of clay and salt without reaching bedrock. Each pair 
of salt and clay layers represents the evaporation of a lake, the salt 
representing the final product as the water disappeared. 

In the middle part of Death Valley, principally north of the road 
leading to Stovepipe Wells, is a small group of sand dunes made up 
largely of quartz sand. 

Considerably north of the sand dunes and only a few miles from the 
famous Death Valley Scotty 's Castle are the Ubehebe Craters, a group 

of small cones built by explosive eruption of fragments of basaltic 
lava. Probably these cones overlie one of the faults traversing the 
graben bedrock, and were erupted only a few hundred years ago. 
The craters in the tops of the cones are well presers'ed and in their 
walls the various layers of fragments blown out by the different ex- 
plosions are well marked. The volcanic cycle seems to have been a 
brief one, as is normally the case with volcanoes built solely by 
explosion. In the southern part of Death Valley there has been liberal 
outpouring of basaltic lava along the faults. 

Cenozoic deposits present in the valley are especially notable for 
their high coloring, as for example along the base of the Black Range 
south of Furnace Creek Inn, where a striking badland area has been 
developed by the occasional torrential storms. Because the rocks are 
quite unprotected by vegetation and surface slopes are steep, the sheet 
and flash floods are literally ripping the deposit to pieces. A labyrinth 



[Bull. 158 

I-'k;. .'n. Sand diinps near Stovppiiip WpHs in l>ert(h Valley. The dunp.s are com- 
IMi.sed nf loose sand drifted o\ er the ari'a \>y wind, and piled a;,' ol>.stacles, even- 
tiiall.v coxerin;: them. I'holo voitttfjtii Stttunial I'ork Servirc, 

of deep, narrow gorgres lies between high, sharp-crested ridges. Most 
of the sediineiits are brilliant yellow in color but there are many other 

In the Tertiary deposits are the famous borax minerals mined long 
a<ro and transported by the plant wagons drawn by the twenty-mule 

Panamint Valley is a narrow faidt basin about 60 miles lon<r lyin^' 
beyond the mountains borderin<r the west side of Death Valley. About 
15 miles from the northern end, alluvial fans built out from the raiifri-s 
on the two sides have coalesced, dividing the basin into two parts 
.separated b.v an alluvial ridjre. At the southern end, this praben is 
narrow, less than a mile across near the San Bernardino Count.v line, 
and not more than 2 miles wide for some distance to the north. The 
alluvial slopes rise steeply to the mountains on both sides. Farther 
north, near Ballarat, Panamint Valley widens to about 10 miles and 
maintains this approximate width for a considerable distance, beyond 
which it again narrows. 

■•^i, '-*«?" <4i 

V i 


Itadland area south of Kurnaoe f'reek in Death Valley National Monu- 
ment. Photo fourteay Motional Park Sm'ice. 

KIG. .";4. I'lieii.l.i I i;,t. ,, ,n i!,r 1, ,: ., : :, , ,1 ,,f Ke^lh Vjille.v. I.a.vcrs ..f hiVii fni 
meota vrupted durint; each explosiun shuw in the <Tater walls. Photo by Wiltard. 

At the south, the west border of the valley is the Slate Range which 
farther north (about latitude .'JG") merges with the Argus Mountains. 
At the southern end the eastern border is formed by Brown Mountain 
which gives way to Wingate Pass 8 miles northward. This is a low, 
nearly level valley about 2 miles wide which slopes gently eastward 
for several miles and then drops rather sharply into Death Valley. 




The summit of the pass is less than 300 feet above the Panamint Valley 
floor, but the mountains to the north and south rise several thousand 
feet higher. North of Wingate Pass, the eastern side of the valley abuts 
against the great Panamint Range, whose high point, Telescope Peak, 
is 11,045 feet above sea level. 

The lowest part of Panamint Valley is a playa or intermittent lake 
about 17 miles long and 3 miles wide at its widest part. This flat is 
nearly a thousand feet lower than the lowest part of the valley at its 
south end and about 600 feet below the alluvial divide which separates 
the valley into two parts. During the glacial stages a large lake was 
present in Panamint Valley. There are wave-cut terraces and deposits 
of tufa standing several hundred feet above the valley floor. Panamint 
Lake was contemporaneous with Searles, the greater Owens, and other 
lakes in the western desert countrj-. Searles Lake at one time appar- 
ently overflowed into Panamint Lake and was in part responsible for 
the notable size and depth of the latter. However, there is a consider- 
able area of mountainous country tributarj- to Panamint Valley and 
the increased rainfall and snowfall over these heights during the 
moister episodes must also have provided sufficient water for a lake 
of moderate size. The uppermost terraces cut by the waves are not 
distinct, hence it has not been possible to determine just how high the 
water rose on the mountain slopes. Tufa has been found at elevations 
as high as 1,980 feet, which is practically that of the summit of Wingate 
Pass, and it is possible that for a time water did flow through this 
break in the mountain barrier into Death Valley. If the maximum 
depth of Panamint Lake was governed by this overflow area into Death 
Valley, the depth of water was about 930 feet and the area roughly 
272 square miles. Not onlj- was the southern part of Panamint Valley 
covered, but the water overtopped by about 300 feet the alluvial divide 
which now isolates the northern from the southern section. This great 
body of water evidently existed for a considerable time in what is now 
desert land. 

No saline deposits comparable with those of Searles Lake have been 
found in Panamint Valley, the deposits formed in it being fine clay 
and sand. 

One exceedingly interesting section of the Basin-Ranges is Searles 
Lake Valley, a rather narrow, elongate depression almost conjpletely 
enclosed by mountains. The boundarj' of the northern half is the Slate 
Range which rises 3.000 to 4,000 feet above Searles Lake and attains 
a maximum altitude of 5,565 feet above sea level. South of this range, 
the border of the valley bends to the southwest and is composed of high 
hills extending as far as Klinker Mountain. These hills are along the 
Garlock fault and undoubtedly have been evolved by movements along 
this zone. The western border of the valley as far south as Salt Wells 
Canyon is formed by the Argus Range, and south of this there is a 
lower unnamed range. 

In Searles Valley there was a large lake or series of lakes during the 
glacial stages of the Glacial epoch, while today there are only a few 
inches of water during the rainy season, hence present Searles Lake 
is an intermittent lake or playa. Evidence of the greater water body 
is provided chiefly by wave-cut benches on the mountain sides up to 
640 feet above the valley floor, at an elevation of 2,262 feet above sea 
level. When the lake reached its highest level, it extended westward 
through Salt Wells Valley and covered a large area in Indian Wells 
Valley. The lake at this time overflowed southeastward also into Pilot 
Knob Valley and thence into Panamint Valley. 

Other evidence of the expanded lake is provided by deposits of the 
porous lime rock, called calcareous tufa, which was precipitated from 
the waters. In places the tufa merely coated other rock, but in some 
localities it accumulated to considerable thickness. It is especially well 
developed at the Pinnacles which are steep-sided knobs rising about 
100 feet above their surroundings some 15 miles south of Trona, near 
where the railroad turns to the southwest. Similar masses also show 
IJ miles southwest of Salt Wells, a short distance east of the canyon 
road to Randsburg. 

Unique features associated with ancient Searles Lake are the saline 
deposits underlying part of the area ; they are outstanding both in the 
purity of the salt beds and also in the variety of minerals composing 
them. Also, there is an unusually high content of potash, for which 
the deposits are worked. The salt body extends to depths of 60 to 100 
feet in the central part of the playa. Laterally it grades into clay and 
sand containing less and less salt, which, in turn, pass into the coarser 
alluvial sediments along the margin of the valley. 

When largest, ancient Searles Lake covered an area of about 285 
square miles. It was one of a system that existed in Owens Valley and 
farther south during the moister climates coinciding with the cul- 
mination of the glacial stages. Most of the water came from the east 
side of the Sierra Nevada, forming Owens River, which ran to the lower 
end of Owens Valley where it was impounded to form a lake much 
larger than present Owens Lake. The water finally overflowed south- 
ward making a stream which ran into Indian Wells Valley where it in 
turn was backed up behind a low barrier forming a small lake. This 
overflowed into Salt Wells Valley and thence into Searles Valley. 
As pre\-iously noted, Searles Lake became too high for its barrier, 
spilling into Panamint Valley where it contributed to a lake that for 
a time was 930 feet deep. At this stage, Searles Lake water also flowed 
into Salt Wells and Indian Wells valleys. Over large areas the surface 
of the Searles playa is characterized by the remarkable self-rising 
ground produced by the formation of salt crystals from water evap- 
orating in the sediment. Alkali crusts are present in places on this 
ground, increasing in continuity toward the center of the playa. 



[Bull. 158 

Fio. 56. Map showing priocipal 
physical divisions of the district south 
of Mono Lake on the east side of the 
Sierra Nevada. After TT. C. Putnam. 

Mono Basin 

One of the most interesting and spectacular parts of California is 
that in the vicinity of Mono Lake which lies in a fault basin at the base 
of the east central part of the Sierra Nevada. This area is about 360 
miles north of Los Angeles and 180 miles east of San Francisco. It is 
traversed by Highway 395 from which three roads branch off. One 
leads across the desert basin to join Highway 6 at Benton Station near 
the Nevada border; the second ascends the Sierra Nevada through 
Leevining Canyon reaching the crest of the range at Tioga Pass and 
then goes down the western slope through Yosemite National Park ; 
the third is a short stretch going past June Lake and back to High- 
way 395 through Reversed Valley. 

The relief of this section is striking, for on the west the great bat- 
tered fault scarp forming the eastern face of the Sierra Nevada rises 
more than 6,000 feet above the desert basin. The scarp is broken by 
deep canyons which are separated by narrow, ragged ridges. In con- 
trast, the relatively flat basin stretches for miles to the east where it 
abuts sharply against various ranges of the Basin-Ranges province. 
In this fault basin three divisions may be recognized : Mono Lake and 
the associated lake plain, the morainal belt, and the Mono-Inyo craters. 

The present Mono Lake is fairly large, measuring 14 miles in length 
by 10 in width, the greater dimension being in the east-west direction. 
The greatest known depth, recorded in 1889, was 132 feet between 
Paoha Island and the Mono Craters to the south. The present depth 
probably is somewhat greater, though the lake level is falling and 
probably will continue to faU because of withdrawal of water from 
tributary Rush and Leevining Creeks for the aqueduct supplying the 
City of Los Angeles. The lake water which contains sufficient concen- 
tration of various salts to make its taste unpleasant, has a foul odor. 

Clearly defined beyond Mono Lake are old shore lines which show 
its much greater size and depth during the culmination of at least two 
glacial stages. In 1947 the surface of the lake stood 6,416 feet above 
sea level ; easily recognized older shore lines stand as much as 654 feet 
above this elevation and a fainter one, less certainly identified, is about 
100 feet higher (between 7,170 and 7,180 feet). When at its largest 
size, this greater Mono Lake, which is called Russell after the geologist 
who first worked out its history, was about 900 feet deep. The shoreline 
at 7,000 feet appears to mark the stand of the lake during the later 
part of the last glacial stage; the higher, less distinct one belongs to 
an earlier part of the same stage. 

Field evidence indicates that Lake Russell overflowed into Adobe 
Valley when it reached its greatest size, but not during the last rise. 
The outlet cut a channel in basalt across the Mono Basin divide 
at approximate elevation of 8,1.50 feet, east of the now abandoned 
Benton-Bodie stage road, and this channel connects with Adobe Val- 
ley by a number of linking, shallow basins and finally by a deep, narrow 
canyon also eroded in basalt. In the eastern part of Adobe Valley there 
is a chain of lakes which appears to be part of a once-connected drain- 
age system. Adobe Valley is linked with Owens Valley farther south 
by a narrow channel in the Benton Range, west of Benton, Nevada. 
Thus it appears that, during the highest rise of Mono Lake waters. 
Lake Russell was the northern end of a chain that extended through 
Owens Valley by way of Searles and Panamint lakes to that in Death 
Vallej' (Manly) which has already been described. 

As the waters of Lake Russell receded to their present position, they 
left a broad area covered by deposits which had been accumulated on 
the floor of the lake. This area is called the lake plain, but actually it is 
a succession of terraces which are clearly defined to an elevation of 





iSln J 

^' « -^ 


■ —'v V Tioga Lodge 


I o 

I I I I i 

5 Miles 

Fio. f>7. Mono I>ake on the cast side of the Sierra Nevada below Tioga Pass. Around the lake are 
the terrace deposits and wave-cut cliffs left by former Lake Russell. /l/(er /. V. Rutselt. 




[Bull. 158 

about 650 feet above the present surface of Mono Lake. In places the 
terraces were eroded by waves into the Sierran bedrock or into mo- 
raines which had been left by glaciers descending from the great 
range; elsewhere they were constructed of sediment deposited while 
for a time the lake stood at various levels and then were exposed as 
the waters fell to lower positions. Most of the debris which tributary 
streams carried into the lake is silt (very finely divided rock frag- 
ments), the remainder being sand and gravel. There is almost no clay 
in the deposits. The lake terraces now are a rather desolate area covered 
principally by sage brush. 

The small town of Leevining at the junction of the Tioga Pass road 
and Highway 385 stands on one of these terraces, a wide one, 380 feet 
above Mono Lake and the same terrace makes the broad expanse of 
Pumice Valley farther south. 

Streams flowing from the Sierra Nevada into Mono Lake, such as 
Rush and Leevining, have cut gorges 300 feet deep into the terrace 
deposits since the recession of the valley glaciers evolved during the 
fourth glacial stage. 

In the Mono Lake region on the Sierran side four glacial stages have 
been recognized by moraines left as the various glaciers receded. 
Records of the last two, the Tahoe and succeeding Tioga, are far better 
preserved than those of the earlier pair, for the later glaciers destroyed 
or greatly modified the earlier deposits. 

Lateral moraines project from the mouths of the larger canyons, 
extending beyond the base of the Sierra Nevada as a series of crescentic 
ridges whose slopes are broad and culminate in narrow crests. Some 
of the embankments rise at least 800 feet above the lake terraces which 
they nearly surround. There are also terminal moraines belonging to 
the last glacial stage but they are small as contrasted with the lateral 
banks. The moraines are chiefly granitoid debris, including great 
boulders embedded in masses of sand and gravel. The extent of the 
morainal belt and the volume of debris included in it is striking testi- 
mony of the vigor of glacial erosion. 

One of the most remarkable topographic features of this area is the 
anamolous horseshoe valley of Reversed and Rush creeks, which is 
jjartly occupied by four lakes, June, Gull, Silver, and Grant. The name 
Reversed Creek is appropriate, for the creek flows from Gull Lake 
toward the mountains rather than toward the low country as does the 
normal drainage ; it joins Rush Creek at the bend of the horseshoe, and 
Rush Creek flows to Grant Lake in the western arm of the loop. June 
Lake has no outlet except a small drainage canal cut across the marshy 
ground separating it from Gull Lake. 

The origin of this strange valley pattern has been explained in 
various ways. Two principal fault systems cross the area, an outer one 
which is the main boundary system along the eastern base of the Sierra 

Nevada and an inner one which runs along the escarpments of Mount 
Parker, Mount Wood, and San Joaquin Mountain, and under the 
trough occupied by Silver Lake. This second system probably has 
been the more important in the evolution of Reversed Creek-Rush 
Creek canyon. It is assumed that two eastward flowing streams crossed 
the area and were separated by a low divide near the south end of 
present Silver Lake. A tributary of one of these streams, eroding head- 
ward along the weak crushed zone of the inner fault system, diverted 
the other stream into itself. The probability is that Rush Creek (the 
western stream) captured Reversed Creek which lies to the east because 
it had the advantage of working in less resistant rock. Whether or not 


■ EOGW «£*■£»». .'* 

Fio. 58. Map of Mono cones and surrounding area. A/(er n*. C. Putnam. 




the capture was made before the end of the next to the last (Tahoe) 
glacial stage has not yet been determined. 

The problem of the reversal of drainage direction appears to be 
related to the relative resistance of the bedrock in the area and the 
relative erosional efficiency of the two branches of the Rush Creek 
glacier. Rocks in the June Lake area are more resistant than those 
about Grant Lake, hence glacial attack upon the former was less effec- 
tive than on the latter. The June Lake branch of the Rush Creek glacier 
averaged about 2.2 miles in length, as compared with the Grant Lake 
arm which was only 1 mile ; the latter not only was thicker (1,800 feet 
as compared with 1,300 feet), but had the advantage of being concen- 
trated in a narrow, well-defined channel. Therefore glacial erosion 
was more successful in the Grant Lake than in the June Lake branch 
of the glacier. The depth of glacial erosion also is closely related to the 
fracturing of the rock, the trough at Silver Lake being deeper where 
the faulting and jointing has been most intense and shallower where 
the ice traveled over rock in which the joints are widely spaced, as 
immediately west of Gull Lake. Thus the valley was deepened less in 
the June Lake area and more around Grant Lake, causing the present 
Reversed Creek to flow in an abnormal direction as compared with 
other streams in the region. 

Perhaps the most unique feature of the Mono Lake region is the 
range of volcanic mountains called the Mono Craters, extending from 
the south side of the lake for about 10 miles southward, and clearly 
visible from Highway 395. The highest of the mountains stands about 
2,700 feet above the surrounding rolling plain and the range as a whole 
would be quite conspicuous were it not dwarfed by the enormous bulk 
and height of the Sierra Nevada a few mUes to the west. 


Fio. 59. 

Panoramic sketch of the west .side of the Mono cones, showing cones, 
domes, and coulees. After U'. C. Putnam. 

The Mono Craters are a group of pumice cones in most of which 
have risen donics of obsidian (volcanic glass of granitic composition), 
some so bulky that they flowed over the cone walls, advancing upon 
the adjacent plain as short, steep-fronted and steep-sided flows, called 
coulees. The range, which is crescentic in groundplan bending toward 
the east, is divided into three nearly equal parts by the projection of 


Kio. (M). Stages in development of the Mono cones, volcanic domes, and 
coulees. 1, Low cones formed by explosions of rhyolite pumice. 2, Rise of vol- 
canic dome in crater of cone, either flush with cone rim or projeclinp far 
above it. 3, Too hish dome elevation caused part of mass to overflow crater 
rim forming short, thick flow called a coulee, covered with blocks of obsidian. 
After W.C.Putnam. 




[Bull. 158 

the two largest coulees nearly at right angles to the trend of the range. 
The northern of these two principal coulees shows only on the eastern 
side of the mountains, but the southern is divided nearly equally 
between the two sides. 

The Mono Range rises highest near its central part, where three 
turret-shaped domes of nearly equal size are present, the middle one 
forming the highest peak. 

North of the northern coulee, there are five domes and two smaller 
coulees; south of the southern coulee are six domes and four large 
explosion pits. The northernmost dome is isolated from the rest of the 
range, standing about a mile from it and just south of Mono Lake. 
This cone and dome, which is called Panum Crater, is low, the dome 
rising about to the level of the crater wall, from which it is separated 
by a trench or moat. 

The generation of most of the volcanic forms of the Mono Range 
has followed a definite sequence. At first explosions of moderate 
violence formed shallow, bowl-shaped depressions much resembling 
large shell holes. Highly gas-charged lava was blasted out building 
low explosion cones made of pumice fragments. Following the explo- 
sive episode, largely solid, cylindrical columns of obsidian rose in the 
craters, forming domes of various heights. If the domes were suffi- 
ciently elevated, they contained enough liquid — though very sticky — 
lava to cause the rising mass to spill over the rim of the cone, generat- 
ing the coulees which in their outer parts are chaotic jumbles of 
angular boulders. In the north and south major coulees separate 
outpourings coalesced to form more extensive flows. Wlien the domes 
ceased rising in the craters, most of the conduits were sealed. There 
was but one case of renewed explosive activity which produced the 
deep pit called the Caldera at the south end of the chain. This is a 
steep-sided double crater occupying the center of an obsidian dome 
extensively destroyed by explosion. 

Great streams of talus coming from the higher domes have almost 
completely masked the pumice cones in which they rose. The obsidian 
boulders forming the talus were generated by fragmentation of the 
steep domes as they cooled and contracted and also by later frost 
wedging which has further disrupted them. 

Two nearly complete pumice cones may be seen near the summit of 
the Mono Range between the southernmost of the three central domes 
and the south major coulee. The Devil's Punchbowl, near Highway 
395, is a small but well-preserved explosion cone whose crater is about 
1,200 feet in diameter and 140 feet deep ; in the bottom is a small 
obsidian plug about 250 feet across, rising about 40 feet above the 
crater floor. Panum Crater, just south of Mono Lake, illustrates a 
somewhat more advanced stage of dome development. The cone is low, 
but stands out distinctly from the rolUng plain round about. Separated 

from its rim b_\- a deep trench or moat is a steep-sided obsidian 
dome which rose after the preliminary explosions had formed the cone. 
The top of the dome, like that of others, is a wild jumble of spires, 
crags, and loosely piled blocks of obsidian. 

The Caldera at the south end of the range, as previously noted, is 
the product of explosion at the end instead of the beginning of the 
volcanic cycle. This crater is comprised of a large, flat-floored bowl 
open at the west and a small, deep pit blown through the north wall of 
the main depression. Originally it was believed that collapse of the 
dome had developed the depressions, hence the name Caldera; but 
later studies indicate that explosions were responsible. The tops of the 
obsidian cliffs forming the walls of the Caldera are covered by 30 to 50 
feet of volcanic ash and the secondary pit is clearly of explosive origin, 
differing from the larger one only in size. There is no evidence of 
faulting, which should be present if the basins had been formed by 

The volcanic cycle which built the Mono Craters started in late 
Pleistocene time. Explosive activity began during the last high stand 
of Lake Russell for pumice is interlayered with lake sediments, but no 
lake shore lines cut the more recent cones, notably Panum Crater which 
is close to the lake and stands only 150 feet above its level. The explo- 
sion cones at the southwest end of the range were erupted through the 
floor of one of the small late Pleistocene lakes lying mainly to the east 
of the range. Pumice blasted out by the explosions mantles moraines 
of the last glacial stage, but there is no sign of activity today anywhere 
in the range. 

Warner Mountains 

A splendid example of a fault block range in northeastern Cali- 
fornia is the Warner Range, a narrow, rugged mountainous mass 
about 87 miles long which extends from southern Oregon across Modoc 
County, California, into Lassen County. On the east it projects 
slightly into Nevada. At the northern end, the range merges into a 
high plateau between Abert Lake and Warner Valley and does the 
same at the opposite extremity just east of the Madeline Plains in 
Lassen County. The width of the Warner Mountains ranges from 8 
to 20 miles, the narrowest part being slightly north of Alturas, county 
seat of Modoc County. The highest peaks, located southeast of Alturas, 
are nearly 11,000 feet, but most are closer to 8,000 feet. 

The eastern front of the range, rising abruptly from arid Surprise 
Valley, is a spectacular, battered fault scarp along the base of which 
runs the road leading north and south of Cedarville. The northern 
half of the western side, as far south as Fandango Valley, closely 
resembles the eastern front. Fandango Valley is a major embayment 
which almost cuts the range in two, but has no counterpart on the 
eastern side. South of this valley, the western front is much less 
imposing, since the faulting is complex and the mountains rise in a 




Fio. 61. 

i'anum Crater south of Mono Lake and part of the Mono volcanic range. lu I'anum Cr.TUT auJ the une inimediatel.v south, volcanic domes have risen about to 
the level of the crater rim from which they are separated by a narrow trench or moat. 

series of steps, each repre,senting a block boiinded by faults. A splendid 
view of the western part of the Warner Mountains may be obtained 
along Highway 395 leading north and south of Alturas. 

The southern half of the western front of the Warner Mountains 
differs widely from the northern. There is no conspicuous escarpment, 
only a long unbroken slope from the base to the crest of the range. 
The surface of this slope for the most part coincides with the upper- 
most layer of lava composing the mountains. 

From the picture just drawn, it is evident that the northern end of 
the Warner Mountains is a horst or vertically elevated fault block 
bounded by battered scarps on both sides ; also that the southern sec- 
tion is a tilted fault block with the great scarp on the eastern side. 
The change from the one to the other is gradual. The uplands of the 
horst are comparatively smooth lava-capped areas, little modified by 
erosion, which are being destroyed by canyons being eroded headward 
into them from both sides of the range. 




[Bull. 158 

Fio. 62. 

I'anorama of the eroded fault scarp forming the eastern side of the Warner Range in eastern Modoc County. The western slope of the range is a gently inclined, 
not greatly dissected erosion surface. Showing at the base of the range is part of Surprise Valley. Photo hy C. W. Cheaterman. 

West of Goose Lake Valley and the north part of Pit River Valley 
is an extensive plateau known as The Gardens. Most of its surface is a 
smooth lava cap but locally small domes of rhyolite and obsidian rise 
above it. Still farther west, toward the boundary of Modoc County, 
there has been much recent volcanic activity and large areas of the 
plateau are covered by lava flows, explosion cones, and other extrusive 
forms. This spntion is known as the Mndnc Lhvh Beds or tlio Burnt 
Lava Country. 

Surprise Valley east of the Warner Mountains is a larger trough 
than that on the western side. Along its eastern margin rises the Hays 
Canyon Range, which is bounded by a battered fault scarp, but one 
far less striking than the eastern declivity of the Warner Range. 

The rocks composing the Warner Mountains are principally lava 
flows and fragmental deposits which lay in essentially horizontal 
position at the time of the elevation of the fault block. These volcanics 
were erupted during a long but intermittent cycle which saw a huge 
section of northeastern California and still greater territory in Oregon, 
Washington, Idaho, and Nevada turned into one of the most gigantic 
volcanic fields of the earth. 

It is believed that prior to the deformation which produced the 
ranges and grabens of this region, an extensive rather even-surfaced 
plain existed. Below this plain the lava flows and fragmental deposits 
were essentially parallel with its surface. Over some sections very late 
basalt flows were erupted, covering them in places to depths of 600 feet. 

Deformation, starting toward the end of the Pliocene or in the 
early pai-t of the I'leistocPiic epoch, pi-iKJuced ii lircnnj dome willi its 
crest in the Warner block; as it evolved the dome fractured. The 
Warner and Hays Canyon ranges rose, while Goose Lake, Surprise 
Valley, Long Valley, and other grabens moved downward. There does 
not appear to have been much compression outside of the broad dom- 
ing, the principal deformation being the differential vertical disloca- 
tions. The evidence for the development of this breaking dome comes 
from the increase in elevation from the Gardens to the summit of the 
Warner Range and the decrease eastward from the summit of Hays 
Canyon Range to its base. In a north-south direction, the greatest 
height of the Warner Range is in its central part with decrease toward 
both ends. The arch in this direction, however, quite certainly resulted 
from differential elevation of blocks bounded by faults and not from 




compression. The Warner Range, therefore, is a mosaic of fault- 
bounded masses which have behaved in different fashions as the 
deformation proceeded. 

Indication of continued sinking of the grabens comes from the 
location of lakes against the base of the steepest escarpments, where 
apparently the movement is most active. If this dislocation were not 
still going on, erosional waste from the ranges which forms alluvial 
fans and aprons at their bases would long since have forced the lakes 
farther outward and the deepest parts of the grabens would be toward 
their centers. The broad playas of Surprise Valley, deposits formed 
in a lake which formerly lay against the base of the "Warner Range, 
Lake Annia in Jess Valley, Alkali Lake in Long Valley, High Rocky 
Lake in High Rocky Valley, Abort Lake, and others hug the steep 
escarpments. All of this evidence testifies to the recency of evolution 
of the major features of this remarkable landscape. 

Surprise Valley, the graben between the Warner Range and fault 
block mountains to the east, starts 7 miles south of the Oregon border 
on the east side of the Warner Mountains and extends for about 54 
miles southward. An average width of about 8 miles is maintained 
over this distance, though there is narrowing at the northern and 
southern ends. At present there is no outlet from the valley. 

Perhaps the most notable feature is evidence of series of large 
lakes called Surprise Lake, which existed during one or more of the 
recent glacial stages. These great bodies of water which reached a 
maximum depth of 550 feet not only filled practically all of Surprise 
Valley but overflowed a narrow divide at its southern end, covering 

Duck Flats. Evidence seems to indicate that at least two lakes were 
separated by a time of aridity, when the valley became very dry and 
probably all of the water was evaporated. The old shore lines are 
indicated by wave-cut cliffs and terraces, and by delta and other 
deposits. The highest shoreline is particularly well marked and extends 
around the valley in virtually undamaged condition. 

The Duck Plat extension spread mostly over a surface of basalt 
which probably already had on it a growing lake, for this area also is 
an entlo.sed basin. In Duck Flat the highest level shore line is best 
developed, indicating that at this stage the lake remained relatively 
stable for a considerable period. Whether the water overflowed bar- 
riers into other basins is not known, though this is quite possible. 

As the water of Lake Surprise lowered, the Duck Flat section was 
isolated from the main body as is shown by an outlet gorge cut between 
the two with the slope toward Duck Flat. For a time two lakes existed 
with that in Duck Flat standing about 200 feet below that in Surprise 
Valley, but wlioii Lake Surprise was still 200 feet deep, overflow 
through the gorge into Duck Flat ended and its lake probably dis- 
appeared rather soon because it seems to have been maintained prin- 
cipally by water from the larger body. Finally the main lake itself 
was completely evaporated. 

On many maps of Surprise Valley, three large lakes are shown 
which are called by some Alkali Lakes and by others Upper, Middle, 
and Lower Lakes. The northern or Upper Lake when filled is a unit. 
Middle Lake also was a unit when it contained water, but, some years 
ago, it was divided by the construction of a causeway east from Cedar- 

li.!. Tauuruma of Fundango Vallij-, a structural J.jprcssion obliquely crossing part of the Warner fault block range in eastern Modoc County. Cross faulting apparentlj- 

has be«a the principal cause of the formation of the valley. Pkolo bii C. W. CAettn-nxin. 



[Bull. 158 

Fio. 04. Pinnacles eroded in volcanic rbyolite tuff in the Warner Mountains. Most of the rocka of the raiifje are basalt tiows. Photo by C. W. Chestcrman. 




Western fciTTyTTi] Hummocks [ H 5<i«J Dun. [1111 'iDetntal I' t ' (I flrn^ilonJ. 

Il~ 5k>p« LliiiiU Surfoce E I Surface LillUAproo |, 1 j l|Or<.,slor.d» 

JVolleij 5lofw3 


Scale ?'?>;! 

Fig. 65. Map of Surprise Valley and the adjacent Warner and Hays Canyon Ranges. After R. J. Russell. 

ville, the principal town in Surprise Valley. The southern or Lower 
Lake, in contrast, is an aggregate of smaller lakes, each of which is a 
playa but does not become dry simultaneously with the others. Since 
the waters of the larger lakes evaporate so that only isolated depres- 
sions are filled, it has been customary to give names to the small 
residuals. Thus the term Eagleville Lake is much more significant in 
Surprise Valley than Lower Lake and refers to a small portion near 
the town of Eagleville. This lake is said to have dried up only once in 
the memory of many of the oldest inhabitants. 

Upper Lake when filled is about 13 miles long and 4 miles wide, an 
overflow channel into Middle Lake preventing further growth. In 
normally wet years, it decreases to about half its major size during 
the dry season, but in dry years it disappears. In the winter the 
frozen surface of this lake often serves as a highway between Lake 
City and Fort Bidwell. When completely dry, the playa surface is also 
used for traffic. L'pper Lake normally does not become as completely 
dry as the two lower ones. 

Middle Lake is nearly as wide as the upper one and is 18 miles long. 
The northern 4 miles have been isolated by the Cedarville causeway 
and is dry most of the time during the summer. The main lower part 
generally contains water until early summer and one or two pools 
usually remain along its western margin. 

Lower Lake is much smaller than either Middle Lake or ITpper Lake. 
Toward the south is a broad, continuous playa but northward this is 
broken, chiefly because of wind-blown accumulations which form 
isolated basins. Nearly everv vear water overflows from Middle into 

the Lower lakes, but during the summer most of the basins are dry. 
However, even in the driest years, a few depressions in the western 
side of the largest playa contain water coming from nearby hot springs. 

Evaporation of the lakes is accompanied by westward movement of 
the eastern shoreline until finally no water is left. When the playa beds 
are exposed, they crack into blocks having an irregular hexagonal 
pattern. In the summer frequent wind whorls carry dust to heights 
of LOGO to .'5.000 above the playa surface, and more violent blows 
cause dust storms which obscure the landscape to elevations of 2.000 
to .3,000 feet above the valley. of the playa beds salt and alkali coatings are abundant; else- 
where there are none. Along the ea.stern side of these salt flats there 
are hunmiocky areas which appear to be wind-blown accumulations 
of sand and dust with deposition starting mostly around sage brush. 
Small, actively migrating .sand dunes are found east of this hummocky 
area. They do not exceed 30 feet in height, and their northeast-south- 
west crests with the steeper slope on the eastern side indicates predonii- 
nantl.v .southeast-blowing winds. 

On the west side of the Hays Canyon Range there is a prominent 
alluvial apron having a slope in the steeper parts of at least 10 degrees. 
Recent fault scarps break the continuit.v of the apron in a number of 
places. Above the alluvial .slope rises the eroded Hays Can3-on fault 
scarp which is steeper, more barren, and more subject to considerable 
rockslides than is the Warner Range across the valley. Thes? notable 
slumps and scars appear to be a product of the deficiency of vegeta- 
tion over the upper slopes of the range which receive much less snow 



[Bull. 158 

and rain than do the Warner Mountains. The elevation of the two 
ranpes is approximately tlie same and the roek formations are alike. 
At the ends of the "Warner Range where the elevation is less and there- 
fore vegetation not so prevalent, slide features are more common than 
in the higher part. 

Along the Warner Mountains across Surprise Valley there also is 
a considerable alluvial apron, with steep slopes (up to 10 degrees) at 
and near the canyon mouths but decreasing farther out until they 
seem almost flat. 

At various places in the Warner Mountains there are a number of 
landslide lakes which have been formed by the collapse of lava rim 
rocks overlying more easily weathered and eroded material. Under 
proper conditions where there is not too much protecting talus, the 
canyon walls are suflSciently exposed so that the resistant rims are 
undermined and masses eventually break loose, cascading into the 
bottom of canyons where they may form dams sufBciently durable to 
impound lakes for considerable periods. 

One example, Clear Lake, located in Mill Creek Canyon 2 miles 
nortlK'ast of Jess Valley in the southeastern part of the AVarner Range, 
is small and not over 90 feet deep. It has been formed by two slides, 
one from each side of the canyon a thousand feet deep. The slide scars 
are so fresh and the delta formed by the stream flowing into the lake 
is so small that the barrier probably was not formed more than 100 
years ago. Blue Lake, 10 miles farther south, is similar in origin and 
very recent, but its waters are impounded by a single slide. Both Clear 
and Jess lakes drain to the Pit River. On the eastern side of the range, 
7,400 feet above sea level, is Lost Lake, also in a deep canyon ; the scar 
of the slide which holds back its waters is much less distinct than those 
of the lakes previously mentioned and the delta plain formed by the 
stream supplying the lake is half again as large as the water surface, 
hence it is considerably older. 

Jess Valley is believed to be a filled, drained, older, and larger 
landslide lake in the valley of the Pit River between Clear and Blue 
Lakes, where the river flowing from the west base of the Warner 
Range cuts a gorge through another up-faulted lava bed block of 
lower altitude. The nearly even surface of the valley is about 6 miles 
long and more than 2 miles wide. The slide which dammed up the river 
is of enormous size. 

Eagle Lake, 30 miles northwest of Honey Lake and therefore south 
of the Warner Mountains, stands about 5,100 feet above sea level, is 

12 miles long and 2 to 4 miles wide. The barrier forming it appears to 
be a landslide on the southeast side. The level of the lake rises and 
falls without regard to rainfall and when it sinks streams flow from 
the outer slope of the barrier and are tributary to streams entering 
Honey Lake. This indicates the porous nature of the dam, a feature 
characteristic of landslide jumbles, but it also shows that the passages 
through which the water emerges are alternately opened and closed. 


Baker, C. L., Physiography and structure of the western EI Paso Range and the 
southern Sierra Nevada : Univ. California Dept. Geol. Sci. Bull., vol. 6, pp. 117-142, 

Blackwelder, Eliot, Lake Manlv, an extinct Lake of Death Valley : Geog. Rev., 
vol. 23, pp. 464-471, 1933. 

Blackwelder, Eliot, Yardangs: Geol. Soc. America Bull., vol. 45, pp. 159-168, 

Gale, H. S., Notes on the Quaternary lakes of the Great Basin with special 
reference to the deposition of potash and other salines: U. S. Geol. Survey Bull., 
vol. 540, pp. 540, pp. 3!)9^0C, 1914. 

Kesseli. J. E., The origin of June, Gull, and Silver lake valleys. Mono County, 
California : Jour. Geology, vol. 40. pp. 726-734, 1932. 

Knopf, A., and Kirk, E., A geological reconnaissance of the Inyo Range and the 
eastern slope of the Sierra Nevada, California : U. S. Geol. Survey Prof. Paper 
110, 1918. 

Lee, C. H., An intensive study of the water resources of part of Owens Valley, 
California : U. S. Geol. Survey Water-Supply Paper 294, 1913. 

Louderback, G. D., Period of scarp production in the Great Basin; Univ. Cali- 
fornia Dept. Geol. Sci. Bull., vol. 15, pp. 1-44, 1924. 

Louderback, G. D., Morphologic features of Basin Range displacements in the 
Great Basin : Univ. California Dept. Geol. Sci. Bull., vol. 16, pp. 1-42, 1920. 

Mayo, E. B., and others. Southern extension of the Mono Craters, California : 
Am. Jour. Sci., 5th ser., vol. 32, pp. 81-97, 1936. 

Noble, L. F.. Structural features of the Virgin Spring area. Death Valley, Cali- 
fornia : Geol. Soc. America Bull., vol. 52, pp. 941-1000. 1941. 

Putnam, W. C, Quaternary geology of the June Lake District, California : Geol. 
Soc. America Bull., vol. 80, pp. 1281-1302, 1949. 

Russell, I. C, Quaternary history of Mono Valley, California : U. S. Geol. Survey 
Eighth Annual Report, pp. 26-394, 1889. 

Russell, R. J., Landslide lakes of the northwestern Great Basin : Univ. California 
Publ. in Geography, vol. 2, pp. 231-254, 1927. 

Russell, R. J., The land forms of Surprise Valley: Univ. California Publ. in 
Geography, pp. 323-3.58, 1927. 

Russell, R. J., Basin range structure and stratigraphy of the Warner Range, 
northeastern California: Univ. California Dept. Geol. Sci. Bull., vol. 17, pp. 387- 
496, 1928. 

Von Engeln, O. D., Ubehebe Craters and explosions breccias in Death Valley, 
California : Jour. Geology, vol. 40, pp. 726-734, 1932. 




As used herein the term Mojave Desert province applies to the area 
in southern California which has the following boundaries : the Basin- 
Ranges province on the north (see pi. 2) ; the southern end of the 
Sierra Nevada and the Tehachapi Mountains on the northwest ; on 
the southwest the Sawmill and Liebre Mountains, the Sierra Pelona, 
and the San Gabriel Mountains ; on the south the San Bernardino 
Mountains and the Colorado Desert. The northern margin is difficult 
to determine, as the Mojave Desert merges into the Great Basin. How- 
ever, an approximate line has been chosen between the southern part 
of the Great Basin where the mountain ranges are markedly parallel 
and the region to the south where the ranges are lower, more deeply 
dissected, and lacking in conspicuous parallel arrangement. This east- 
west line falls between the Nopah and Kingston Ranges and runs west 
to El Paso Mountains north of the mining camps of Randsburg and 
Johannesburg (see pi. 2). 

The Mojave Desert is characterized by a small amount of annual 
precipitation and low humidity. The temperatures are moderately 
high in the winter and extremely high in the summer, with notable 
daily range. At certain times of the year strong winds blow across the 
region. Precipitation increases with altitude, but the increase is far 
from uniform, the known differences in part at least resulting from 
position of a locality with respect to the rain-bearing winds. 

Faulting has been conspicuous in the Mojave Desert province and 
has been the prime control of separation of high- and low-standing 
areas. Most notable of the fault systems is the San Andreas which lies 
along the north base of the San Gabriel Mountains. It shows con- 
spicuously from the air as an almost continuous succession of long, 
narrow basins separated by elevated areas which undoubtedly are 
small fault blocks that have risen as the basins have subsided. The 
last known dislocation along this section of the rift occurred in 1857. 

Another prominent fault system, the Garlock, is found along the 
southeast face of El Paso Mountains. Near the town of Garlock, it cuts 
a large alluvial fan ; 5 or 6 miles to the northeast, near Goler Well, 
there are large depressions formed by dropping of blocks of ground 
along the fracture zone. The scarps are so fresh that the dislocation 
must be rather recent. Northeast of El Paso Mountains, the Garlock 
fault shows along low hills on the south border of Searles Valley. East 
of the Slate Range, a long, narrow valley — with Leach Point Moun- 
tains rising steeply on the southern side and a more gentle slope on the 
northern — suggests the same fault, which may contintfe as far as the 
Avawatz Mountains. However, the faults in the Avawatz Mountains 
may belong to another series. Southwest of El Paso Mountains there 
is a marked escarpment on the southeast side of the Tehachapi Moun- 

tains which is in almost perfect alignment with the southetist side of 
El Paso Mountains, containing sag ponds and other features showing 
that the Garlock fault continues in that direction. 

The San Andreas rift and the fault along the front of El Paso and 
Tehachapi ranges bound a conspicuous area having the form of an 
arrowhead, whose point is at the western edge of the desert. This area 
has within it only low, scattered hills but no large mountains. 

South of the Garlock fault, the strikingly parallel ranges and basins 
so characteristic of most of the Basin-Ranges province are less appar- 
ent, and the arrangement in most of the Mojave Desert is much less 
clearly defined. However, there is abundant evidence of faulting in 
many places, and major landscape features have been evolved by 
movements along the faults, many of which seem to be rather short, but 
have been zones of much displacement. 

Areas where faulting seems to have exerted notable control in land- 
scape evolution are Lane Mountain and the connected hills about 15 
miles north of Daggett ; the basins containing the playas known as 
Soda, Silver, and Silurian dry lakes, with the adjacent mountains 
extending from the Soda Lake Mountains north to Avawatz Mountain 
and the New York-Providence Mountains. Others are a series of north- 
westward trending, short, parallel ridges north of Bagdad and Amboy, 
the highest of which is Old Dad Mountains, and a more or less con- 
tinuous range south of the Atchison, Topeka & Santa Fe Railway, 
extending from near Daggett for many miles southeastward and 
including the Bullion and Sheep Hole Mountains. 

Evidence is insuflScient to determine the age of much of the faulting 
but some certainly is of verj' late date and some faults are still active. 

Because most of the Mojave Desert has not been studied geologically, 
the history of its landscape is imperfectly known. 

The Afton Basin is an enlargement of the valley of the Mojave 
River about 40 miles east of Barstow in the Mojave Desert. This area 
is one of rather even-surfaced alluvial deposits — both low sloping 
alluvial fans and basin sediments — above which rise isolated moun- 
tains of moderate elevation. The basin appears at one time to have 
been undrained, and this condition probably continued into middle 
Pleistocene time. Later the Mojave River, flowing from the San Ber- 
nardino Mountains, advanced into the region where its waters were 
impounded to form Lake Manix, named for a station on the Union 
Pacific Railroad. An almost completely enclosed embayment of this 
lake occupied the Afton Basin. Later on, probably because of erosion 
by its outlet, this lake was drained and the sediments deposited therein 
have been eroded rapidly by the Mojave River and its tributaries. 




(Bull. 158 


Fig. 66. Sag ponds, basins. 

and bu.les (cencer, formed by Sao Andreas fault near Palmdale, Mo.ave l.eser,. P>,oto courU.y FaircHili .Unol s„r,ey.. Inc. 





h'lQ. 67. Panorama of the Cbuckawalla Mountains, Riverside County, a fault-block range in the Mojave Desert. Photo bu C. \V. CheMterman. 

Field evidence shows that the basin actually contained two lakes, 
the earlier of which disappeared because of an intervening dry epoch. 
Then a third much smaller lake developed in Mojave River canyon 
after the draining of the earlier lake water and dissection of the sedi- 
ments which had been deposited in it. 

The first lake apparently had a fluctuating level determined by the 
balance between inflow and evaporation. For a time it was relatively 
fresh as the presence of fish remains and moUusk shells proves, but 
later it bciame distinctly saline as is shown by gypsum crystals in 
some of the sediments. Manix and Afton Basins during this interval 
seem to have contained all the water brought in by the Mojave River, 
for had the lake overtopped the divide separating them from the much 
lower Soda Lake basin to the east, the outlet would undoubtedly have 
been cut down sufiiciently to have destroyed Manix Lake. The first 
lake lasted sufficiently long for its waves to build large and rather 
conspicuous gravel bars along the northeast side of the basin. The 
moister interval which made possible the growth of this water body 
probably coincided with the earlier (Tahoe) part of the fourth glacial 

Then the climate seems to have become more arid, the Mojave River 
no longer reached Afton Basin, and the lake water evaporated leaving 
a playa floored by clay. Some minor alterations in the playa surface 
were caused by erosion and deposition. 

Again moister climate returned, this during the later (Tiogan) part 
of the fourth glacial stage, and the second Lake Manix developed. The 
surface rose about 20 feet higher than that of the first lake, and the 
waves, besides making important additions to the gravel bars, cut small 
cliffs and terraces. The new lake overflowed eastward into Soda Lake 
Basin. The outlet dropped about 875 feet in 14 miles and hence was 
a powerfully eroding stream which not only cut a deep notch on the 

east side of Soda Lake Basin, but with its tributaries so extensively 
eroded the floor on Manix Lake Basin that only small remnants of the 
bottom deposits of the first lake remain as divides between the gullies. 
The gravel bars, being farther back from the river and more porous 
in composition, were less affected ; they are still almost intact for per- 
haps half their original length. 

Some time after this badland topography was evolved, a third lake 
appeared in the Mojave River valley, but because its surface was not 
more than 1.637 feet above sea level, it did not extend into Manix 
Basin, was much smaller than its predecessors, and also was shorter 
lived. The cause of the development of this lake has not been dis- 
covered. Since a continuous gorge had been eroded from Soda Lake 
Ba.sin into Manix Basin, the only reasonable explanation is that this 
canyon was blocked in some manner, but no evidence of such barrier 

If the third lake was formed in the manner indicated, it had no 
climatic significance ; the first two. however, seem to be definitely asso- 
ciated with the third and fourth glacial stages. 

In the Mojave Desert, there are a number of places where granite 
and other granitoid rocks exposed in mountain blocks have been 
eroded to form rather smooth, dome-like areas with craggy masses of 
the bedrock standing above the general level and detached boulders, 
some of large size, scattered over the surface. The ragged appearance 
(if the ridges and the boulders has been developed by weathering along 
closely spaced joints. Such domes range from 3 to more than 8 miles 
across and their high points stand from 500 to 2.000 feet above adja- 
cent lower land. Good examples may be seen at various places along 
Highways 66 and 91 east of Barstow. This peculiar landscape appar- 
ently results from the progressive erosion of an elevated fault block 
in which granite forms a considerable part of the bedrock. 



[Bull. 158 


Fio. 68. Tbe Moapi, vok-anic necks of rhyolite in the central part of the Turtle Mountains, eastern San Hernardino County. Photo by V. W. Chemfrmnn. 





Fio. tlQ. Turtle MoutiCiiiUs near ('arsons \\>U. eastern San Bernardino County. The volcanic rocks in wtii^ . -:-< 

that produced the more subdued forms in the foreground. Photo by C. W. Chtstcrman. 

nled overlie ancient grauite 



[Bull. 158 



Kui. TO. West biUe of Rattlesnake Cuiiyuu. Au eruded fault-block mountain in the Mojave Desert. Keiirock is uninite; ragced toi.ography results frnm weath.-rinK and 

erosion alonj; closely spaced joints. Photo courteaj/ National Park Service. 




^"'' '*■ ''n/.''"n'?'"° TT ""^ C»Iof«.<io River. The dam impounds a long, narrow lake, from which water is conducted by the Colorado Aqueduct to a storage ) 
near Riverside. From there, it is distributed to various parts of the Los Angeles Basin and San Diego. Photo courtay V. 8. Bureau of Reclamation. 



[Bull. 158 


Fio. 72. Panorama of the north part of the Turtle Mountains, eastern San Bernardino County. Photo hy C. W. Chetterman. 

Along the California border with Nevada a large man-made lake 
lies behind Parker Dam situated in one of the canyons of the Colorado 
River about 16 miles north of the town of Parker on the Arizona side 
of the river. The great stream has excavated this canyon through one 
of the fault-block ranges of the Mojave Desert, apparently keeping 
pace with the elevation of the block as it has done in crossing various 
other ranges. The dam which rises about 300 feet above the surface of 
the water has impounded a long, narrow lake — a beautiful sight in an 
otherwise desert land. Prom this reservoir water is hoisted by electric 
power brought from the great generating plant at Hoover Dam. Five 
lifts are necessary to carry it over a divide about 1,600 feet above the 
reservoir surface. Prom this point, a transporting system, the Colo- 
rado Aqueduct, carries the water down slope across desert basins and 
by tunnels through mountain ranges to a main storage reservoir about 

7 miles southeast of Riverside. From the reservoir, mains and canals 
lead to various parts of the Los Angeles region and also to San Diego. 
Parker Dam can be reached by an oiled road which branches off 
from Highway 95 about half way between Needles and Blythe. 


Baker, C. L., Notes on the later Cenozoic history of the Mojave Desert region 
in southeastern California : Univ. California Dept. Geol. Sci. Bull., vol. 6, pp. 333- 
383, 1911. 

Blackwelder, Eliot, and Ellsworth, E. W., Pleistocene lakes of the Afton Basin, 
California: Am. Jour. Sci., vol. 31, pp. 453-463, 1038. 

Davis, W. M., Granitic domes of the Mojave Desert : San Diego See. Nat. Hist., 
Trans., vol. 7, pp. 211-258, 1933. 

Foshag, W. F., Saline lakes. Mojave Desert, California : Econ. Geology, vol. 21, 
pp. 56-64, 1926. 

Thompson, D. C, The Mojave Desert region : U. S. Oeol. Survey Water-Supply 
Paper 578, 1929. 



The Imperial and Coachella valleys are parts of a great depression 
of roughly V-shaped groundplan occupying a section of southeastern 
California known as the Colorado Desert province. This immense 
structural trough has its apex to the north not far from where the 
San Jacinto and San Bernardino Mountains meet at San Gorgonio 
Pass through which goes Highway 60 on its way eastward and then 
southeastward from Banning. The trough opens to the southeast 
where it is continuous with the larger and much deeper depression 
occupied by the Gulf of Lower California. Rising more or less abruptly 
from the southwestern and northeastern sides of the Imperial and 
Coachella valleys are bold mountains : the Peninsular Ranges border 
the southwestern margin while the southeastern portion of the San 
Bernardino Mountains of the Transverse Ranges province and various 
elevated blocks belonging to the Mojave Desert province lie along the 
northeastern side. 

The climate over the depressed area is desert, being characterized 
by extremes of heat and dryness, for the Imperial Valley section is 
the hottest part of the United States and one of the hottest in the world. 
Ranges of temperature also are extreme as is characteristic of all such 
regions. The highest recorded temperature was 130°F., the lowest 22°F. 
Rainfall ranges from 1.10 inches annually at Ogilby, a small settle- 
ment in the far southeastern corner of the Imperial Valley, about 16 
miles northwest of Yuma, Arizona, to 3.53 inches at Palm Springs 
^ear the northwestern end of the Coachella section. Most of the mois- 
ture falls in December, January, and February ; in the Salton Sea 
region the month of June is practically rainless. 

The Salton Basin is the southeasternmcst section of the Imperial- 
Coachella trough and, though now separated, it is continuous with 
the depression under the Gulf of Lower California. At one time the 
gulf extended about 125 miles north of its present limit and one arm 
projected into the present Imperial Valley, a considerable section of 
which lies below sea level. The Colorado River discharged into this 
expanded gulf head north of the Mexican border as today it does into 
the shortened gulf south of this boundary. Near the border between 
the United States and Mexico, the river built a huge delta, the land- 
ward part of which finaUy rose above water level as a delta plain that 
eventually extended across the gulf isolating the northern part and 
impounding its waters as a lake having no connection with the ocean. 
As in most of southern and southeastern California, the climate in 
recent time has become increasingly arid causing the drj'ing up of 
the lake and the conversion of the whole of the Imperial-Coachella 
depression into a desert. 

The area of the Imperial-Coachella trough is considerably greater 
than that of other similar areas in California but the major features 
of the landscape are quite similar. The central part of the Salton Basin 
is rather flat. In a number of places bedrock masses project above the 
sedimentary fill, as for example Borego, Superstition, Carrizo, and 
Cargo Muchacho Mountains, Indio Hills, Pilot Knob, and a number 
of volcanic buttes 100 to 200 feet high south of Salton Sea. 

Along the borders of the Salton Basin, there are extensive badland 
areas, as for example in the Mecca and Indio Hills near the two towns 
of those names on the east side and south of the Santa Rosa Moun- 
tains, around Seventeen Palms, and in the valley of Carrizo Creek 
on the west side. Smaller areas are numerous. 

Badlands are areas characterized by a labyrinth of gorges separated 
either by round-crested or sharp-crested ridges. They are a product 
of the various pha-ses of sheet and flash flood erosion in weak rock or 
rock mantle unprotected or insufficiently protected by vegetation. 
While best developed in arid lands, they are found also in humid places 
where for one reason or another the plant cover has been removed or 
seriously depleted. Badlands are among the most intricately sculp- 
tured landscapes. 

The arroyos or dry washes generally are V-shaped in cross section, 
though some of the larger are flat-bottomed. The walls may rise almost 
vertically or may flare outward at various angles. In this region, where 
such landscape has been developed in nearly horizontal strata, ver- 
tically walled, flat-bottomed gorges predominate, and between them 
are nearly flat-topped divides rather than the more normal rounded 
or sharp-crested ridges. It is believed that this shape results from 
the speedy erosion by infrequent flash floods which represent the 
accumulation in brief time of great volumes of run-off. The torrential 
rain falls too fast for any great volume to sink into the ground, hence 
landsliding of water-logged masses from the walls rarely occurs. 

In folded rocks, as in the Indio and southwest part of the Mecca 
Hills, the dry washes follow the outcrops of weak layers in which 
narrow, V-shaped gorges have been cut while in between are narrow 
ridges developed in resistant strata. 

Wind erosion and deposition in this and other desert regions of 
California are no match for the effects of running water, but many 
sections show evidences of both. 

Sand dunes are rather abundant in the Imperial and Coachella 
Valleys, particularly in the Salton Basin. The Sand Hills, running 
from past the Mexican border northward for 40 miles somewhat 
beyond the little settlement of Amos is the largest dune patch in 




[Bull. 158 

Fig. 73. New highway and nl«l phiin. ri.:nl , rn^vm;; die sand .sea in the south- 
eastern part of the Imperial Valley. The main highway is sometimes blocked by 
drifting sand. Fancher's Fotot. 

Fig. 74. Old planl; ron.l iii ^ollll,.■:lMrr■^ |miI .,f liuii. \";illri. .Sand 
has partly blocked the road. Fanchtr's Futos. 

California and one of the largest in the United States. The belt ranges 
from 2 to 6 miles in width, forming a prominent barrier roughly 
paralleling the trend of the great trough. The crests of some of the 
dunes rise 200 to 300 feet above their surroundings. Highway 80 
crosses this most interesting area and is blocked on numerous occasions 
by the drifting sand and an old, now abandoned corduroy road has 
been extensively buried. 

Dunes are built principally by violent winds such as are common 
in desert areas and are best developed where the direction of blow is 
more or less uniform. Study of the Sand Hills shows that the winds 
responsible for their formation have come chiefly from the southwest, 
west, and northwest. West of the Sand Hills there is a nearly level 
plain 3 to 20 miles wide covered practically everywhere with sand 
which in places has piled into small dunes. However, over most of the 
plain is a thin coating of gravel consisting of fragments about the 
size of peas and evidently too heavy for the wind to move. This entire 
deposit is a beach formed when the lake was present in the Salton 
Basin. Probably the Sand Hills began to develop as the beach was 
formed and the supply of sand was being constantly increased. The 
dunes have migrated to their present position as the wind continued 
to blow over them driving the sand eastward, leaving the larger frag- 
ments behind. When this migration occurred is uncertain but land 
surveys made in 1856 show very little difference in form and position 
of the dunes from the present. There does, however, seem to be some 
movement of the hills towards the southeast. 

In the Coachella Valley, north of Indio. there are extensive areas 
of shifting sand which are called drifts, but only around Indian Wells 
are there large dunes, which are formed by strong winds blowing 
from the northwest down San Gorgonio Pass into the heated lowland. 
In the pass itself there are great drifts of sand piled on the east sides 
of all rocky spurs projecting from the San Jacinto Mountains. Drifts 
are distinguished from dunes by being less sharply defined land forms. 

Southwest of the Salton Sea, between McCain and Kane Springs, 
there is an area where small creseentic dunes called barchanes are well 
developed. These sand hills appear to evolve where the wind blows 
quite constantly from one direction and the supply of sand is rather 
meager. The barchanes are strongly unsymmetrical in cross section, 
with the gentle slope oriented in the direction from which the wind 
blows. The horns of the crescent, like the steep side, lie in the opposite 
direction. The sand forming the dunes apparently comes from an old 
beach, practically all of the sand having been used up in making the 
dunes. Some of the barchanes are not more than 300 feet from point 
to point of the horns, others measure about 1,000 feet. Many of these 
dunes travel in the direction toward which the wind blows, others 
have been essentially stationary for considerable periods of time. 
Those in the Imperial Valley have not changed position materially 
for the last 10 or 15 years, but this is quite a brief interval. 

In San Felipe Valley in the same general region where the barchanes 
occur, there are spring-formed dimes. These develop in sandy areas 
where rising seep water allows growth of vegetation on accumulating 





'JtJ'iKSf^'^^ fj". 


Klo. "3. Saud sea in the southeastern part of Imperial Vallej west of Yuma. Arizona, fholo courtesy Sptnce Air Photos. 



[Bull. 158 





sands. The sand may pile so hifrh that the water cannot rise throujrh it, 
and the spring is completely sealed. The core of the dune is a black, 
mucky mass of soil and decayed vegetation. Kane Spring, which 
occupies a mound about 30 feet hi^rh and several hundred feet in 
diameter, is an example. At the top is a sunken marshy area an acre 
or two in extent from which water seeps eastward. 

Peculiar dunes having a serpentine pattern occur on Superstition 
Mountain west of Westmorland on Highwa.v 99 and are elongated 
parallel to the long axis of the mountain. They are found on both sides 
and apparenth' shift back and forth over its crest as wind direction 
changes. Frequently they blockade canyons, forming temporary basins 
behind them. 

In various parts of the Imperial and Coachella Valleys, great 
numbers of irregular sand drifts have formed about clumps of vege- 
tation, rock piles, and other obstructions. 

One of the notable features of the Salton Basin is an old shore line 
which stands 40 to 50 feet above sea level, encircling the Imperial 
Valley including the Salton Sea, that part of the Coachella Valley 
south of Indio, and extending south of the border into Mexico. On the 
west side of the Salton Basin and throughout the Coachella Valley, 
the beach at most places consists of a sand ridge a few feet high, 
though its character varies somewhat with the rocks on which it was 
formed. In the sand are found many small, well preserved fresh-water 
shells. Near Fish Springs the shore line of the lake was granitoid rock 
and there is no beach deposit like that just described. Instead the 
shoreline is marked by an encrustation of the massive, limy rock 
called liaxcrtine which in places is several feet thick. This deposit, 
formed from the evaporation lake water, makes a white zone con- 
spicuous from a considerable distance. 

On the east side of Imperial Valley and as far north as Frink 
Spring, there is an almost continuous wave-cut cliff 10 to 30 feet high, 
with various amounts of sand forming the beach at the base of the cliffs. 

All of these features show the presence of a large lake as one of the 
very recent features of this now desert basin. The shells indicate that 
the water was fresh or nearly so, hence the lake must have been sup- 
plied by the Colorado River which at that time apparently discharged 
into it rather than into the Gulf of Lower California, though overflow 
from the lake very likely went into that arm of the ocean. This lake. 
Lake Cahuilla, may have represented the gradual freshening by the 
Colorado of the arm of the Gulf of Lower California cut off by the 
building of the river's delta plain. On the other hand, the salt water 
may have dried up and the basin later supplied with fresh water from 
the river. Whatever is true. Lake Cahuilla lasted until very late time; 
its waters may have remained until 300 or 400 years ago. There also is 
some evidence that the basin may have been occupied by fluctuating 

lakes for a long time and that on some occasions the water disappeared 
by evaporation, later to be replaced by overflow from the river. 

The basin is known to have been comparatively dry from the time of 
the Spanish discoveries to the time of the great floods of the Colorado 
(1904-07) which created the present Salton Sea. 

As the agricultural value of much land in the Imperial Valley 
became increasingly apparent, the problem of supplying sufficient 
water for irrigation became a pressing one. In 19 00 work was com- 
menced on a canal system to bring water from the Colorado River 
into the basin, and at that time the name Imperial Valley was chosen 
to lure settlers to this desert land. 

• / • — 


Fig. 77. View of Imperial X'alK-y, sh-'wiiii: ih*- pr- 
raised in much desert soil if watt-r is avuilable. J'hoto < 

iti'.' rrnp^ wliich can be 
uurttay i'. .S. Bureau of 

The transfer of water from the great river to the Salton Basin 
seemed quite simple. For years the Colorado had spilled its flood 
waters into the basin through two rather well-defined channels. Alamo 
and New Rivers. The slope from the river down the delta plain into 
the Salton Basin is greater than that toward the Gulf of Lower Cali- 
fornia. The California Development Compan.v. which built the irri- 
gation system, constructed its intake near Pilot Knob, an isolated 
mountain projecting above the alluvium of the delta plain about 
10 miles west of Yuma, Arizona. The water was diverted through a 
gap excavated along the side of the river, and was led through a canal 



I Hull. 158 







Fig. 78. Imperial Valley and Salfon Sea. The Salton Sea haa attained its pres<'nt size primaril.v as the result of great flows from the Colorado River in 

1U05 and 11)06. Photo courtesy Southern Pacific Railroad. 

which crossed the Mexican border and then went back into the Salton 
Basin some distance away. Later, because of too rapid silting in the 
canal, another intake was cut on the Mexican side of the border. 

The flood danger from the Colorado was then not well understood 
and no proper preparation was made to take care of the river at high 
water. In the spring of 1905 several unusually high floods materially 
widened the break made in the river bank for the canal and these 
floods also carried a>vay dams built to seal off this intake. By summer 
time when the highest water stage is reached, too much water was 
being diverted toward the Imperial Valley through the canal and 
spilling over its banks, where it wasted and began the formation of 
the Salton Sea. The irrigation company, involved in financial di£5cul- 

ties, had placed itself under obligation to the Southern Pacific Rail- 
road which finally took charge of the river control. Efforts were made 
to dam up the intakes, but successive floods carried these structures 

Growth of the Salton Sea forced the railroad to move its main line 
to higher ground a dozen times and threatened to engulf all of the 
irrigable land of the Imperial Valley. The water sweeping into the 
basin eroded wide gorges into the soft alluvium, in which are the 
present channels of New and Alamo Rivers. 

After most strenuous effort and great expenditure, the Southern 
Pacific succeeded in closing the break in November 1906, but a flood 
in the following month destroyed the repairs and the work had to be 






\ iilley Kraben showing the borJprinj; > 
iu Lhe backeround. Photo courtety Fairchild Aenal :iut leys. 



[BuU. 158 

na. The buildinE of the rorabined delta and delta plain has sh..rliMied the Gulf 

Ftc. 80. C-olorado River flowing over its <!^;_'«/';j, -f/,f i^^p^,-;;,*^™:; ,;;b,--,-C formerly was invaded by gulf water. Pko,. .ourU.y «pe„ce 

of Lower California by at least 125 miles and 
Air Photos. 

done again. Finally, aided by reduction of the flood waters, the river 
was sealed off and the valley rendered temporarily safe. However, 
what the river had done many times it could repeat, hence agitation 
started for the development of a flood-control project farther up the 
Colorado. This finally was undertaken and Hoover Dam now holds in 

check by far the greater part of the Colorado's floods. Relatively little 
water comes in below this barrier. 

In the evolution of the Imperial-Coachella trough and the bordering 
ranges, faulting has played a paramount role. The depression is part 
of a very large graben which extends southeastward beyond the 




boundary of the Imperial Valley, while the ranges borderinji on the 
east and west quite evidently have been elevated as the siraben has 
sunk. Along the north side of San Gorgonio Pass and extending south- 
eastward into the basin is the San Andreas rift. It probably is con- 
tinuous with a fracture zone extending along the northeast side of 
the Indio and Mecca Hills, both of which apparently have been 
elevated by movements along this section of the fault. These low hills 
rise from the basin floor and are separated from the higher mountains 
to the northeast by a series of valleys and saddles. North of Indio, 
the northeast side of the Indio Hills is quite steep, though not more 
than 200 or 300 feet high, and is the most clearly defined fault scarp 
in this section. West of Dos Palmas the scarp is merely a low bluff. 
The fault probably passes north of low hills near Palm Springs 
Station ; to the southeast it appears to extend at least as far as a low 
hill near Durmid which probably was uplifted in manner similar to 
the hills farther north. The same rift may continue as far as the 
Mud Volcanoes southeast of Salton Sea, and on past the Mexican 
border. Much of this is speculation because of the cover of sediment 
which makes positive identification virtually impossible. 

On the southwest side of the basin there are faults of two ages trend- 
ing in somewhat different directions. The intersection of these systems 
has caused the irregularities in the outline of the western border in 
which great mountain salients like the Santa Rosa Mountains, the 
VaUecito and Fish Mountain spur, and the mountainous projections 
along the Mexican border are separated by deeply re-entrant vaUeys 
like those of San Felipe and Carrizo Creeks. 

If this structural picture is correct, the older of the two fault sys- 
tems trends about 10 degrees north of west and is responsible for three 
spectacular escarpments, one forming the east base of the San Jacinto 
Mountains and passing up Palm Canyon, the second on the west side 
of Borego Valley, and the third extending from Agua Caliente Springs 
southward up Carrizo Gorge along the east face of Laguna Mountains. 

Cutting across this older system, a second system trends approxi- 
mately 45 degrees north of west and is represented by several prom- 
inent faults. The most northerly is the San Jacinto, trending west 
and south of San Jacinto Mountain and extending through Hemet 
Valley, down Coyote Canyon, and for several miles along the north- 
east side of Borego Valley. The uplift along this fault has been on the 
northeastern side and Coyote Mountain, northeast of Borego Valley, 
is part of a prominent spur elevated along the fault and having a 
prominent scarp on the southwestern side. 

Several faults have been recognized near Warner Valley and extend 
southeastward in this part of the region ; apparently developed by 
them are a number of so-called valleys, such as Borego, San Felipe, 
Mason, VaUecito, Collins, and a small one at Banner. Each of these 
valleys has for its northeastern wall a steep face which is a moderatel}' 

battered fault scarp ; the south and west sides are much more irregular 
than the northeast, and the valley slopes are less abrupt. Most of the 
vaUeys are high at the southwest, draining to the northeast as though 
the fault blocks had been tilted to the southwest. 

The faults have compelled the streams in most of the valleys after 
reaching the northeast sides of the valleys to flow southeastward, as 
is illustrated in Coyote, Grapevine, and Banner Canyons. However, 
some streams like Banner and San Felipe have eroded deep gorges 
cutting across the faults, suggesting that the streams were present 
before the faults were developed and that movement along the frac- 
tures was slow enough so that the streams cut downward as rapidly 
as the rocks were elevated across their paths. 

Xortheast of the Salton Basin well-defined faults are difficult to 
make out because of the erosion of the range blocks and the great 
amount of alluvium which has been spread around their margins. 
However, topographic evidence suggests ver>- strongly that the ranges 
have been elevated along fractures. The steep south front of the 
Cottonwood and Eagle ranges northeast of Highway 60 70 and a 
prominent scarp at the south side of the Maria Mountains are examples. 
At the north end of the Palen Mountain east of Desert Center on 
Highway 60 70, there is definite e\'idence of faulting. 

About 16 miles north of Yuma, Arizona, a long low dam, the Im- 
perial, has been constructed across the Colorado River impounding a 
large, shallow reservoir. Great canals carry water from the reservoir, 
one to the California side to supply the Imperial and Coachella Valleys, 
the other to the southwestern corner of Arizona where there is rich 
land in the Gila River basin. The California canal has been constructed 
across the Sand Hills. The main branch gives water to the ImpfTial 
section ; a smaller one leads north into the Coachella Valley. The desert 
soils in many places yield splendid crops if water can be supplied. 
In this highly arid region, the Colorado River is the only sufficient 
supply. Used since the early part of the century, its water is now being 
taken in much greater quantity through this AU-American Canal 

The Colorado River forms the eastern boundary of California from 
slightly southeast of a small settlement in Arizona called Mojave City 
to the Mexican border. Most of its length in this section is bordered by 
mountain ranges, the largest on the California side being the Maria. 
McCoy, Palo Verde, and Chocolate. Depending on the distance of 
ranges from the river, its valley ranges from 2 to 2.) miles in width. 
Tributaries are insignificant because of the aridity of the region. The 
Arroyo Seco, a dry stream channel in the northeastern part of the 
Imperial Valley is the largest, having a length of about 50 miles. 
Elsewhere the mountains are connected by alluvial divides which form 
enclosed basins that do not drain into the Colorado. 



[Bull. 158 

Throughout virtually its entire length along the California border, 
the Colorado Valley is terraced into two parts separated by a promi- 
nent bluff 50 to 100 feet hi^h. The lower terrace is that being developed 
by the river and covered with its sediment when overbank Hoods occur, 
the other represents a former level at which the river flowed. The 
lower terrace, which is called Palo Verde Valley, has a slight slope 
away from the river because of the formation of natural levees along 
its banks, the characteristic feature developed especially by a large 
stream flowing through a lowland region. The surface soil is fine 
textured, and is added to almost every summer by floods except where 
artificial levees have been constructed to contain the waters in the 
normal channel. Numerous old channels and oxbow lakes show the 
usual wandering of the river from place to place over its flood plain. 
The Palo Verde Valley in places is 7 to 8 miles wide, but where the 
mountains come close to the river, as with the Chocolate Mountains 
near Laguna Dam north of Yuma, it is greatly constricted in width 
or even absent. 

The higher terrace, called the Palo Verde Mesa, is a narrow almost 
level plain a few miles in width. In some places, the Palo Verde Mesa 
is broken by bluffs which divide it into a series of terraces standing 
at various levels. West of Blythe, for example, there is a second ter- 
race 30 or 40 feet higher than the first part of the mesa. The surface 
of the terrace in most places is sandy or gravelly, but beneath there 
appears to be finer sediment. However, where good exposures show in 
the escarpment separating the Palo Verde Mesa from the flood plain 
below, sand and gravel predominate. Near mountain borders, the 
terrace rises abruptly and grades into alluvial fans at the mouths of 
canyons. The surface material in such places is coarse sand, pebbles, 
and boulders. 

The escarpment separating the Palo Verde Mesa from the present 
flood plain of the Colorado is quite .straight and has an abrupt slope, 
though it has been considerably notched by sheet-flood and flash-flood 
erosion. On the Arizona side, the terrace bluff is modified by the Gila 
River which joins the Colorado near the Mexican border. The bluff 
along the Colorado merges with a similar one which extends up the 
Gila Valley for at least .50 miles. This would indicate that the escarp- 
ments along the two rivers are similar in age and origin,, 

A particularly notable feature of the blulT on the California side is 
that it bends westward at Pilot Knob, near the international boundary, 
passing south of the Sand Hills on the Mexican side, and then turns 

northward, merging into the old shore of Lake Cahuila which is 
marked by a prominent wave-cut cliff for many miles northward. 

There is striking similarity between the escarpment along the Colo- 
rado River iuiil the escarpments left by the erosion of New and Alamo 
Rivers as the result of the overflow into the Imperial Valley in 1905 
and 1906. For many miles, the gorges cut by these two streams are 
about 50 feet deep and nearly a quarter of a mile wide. The bluffs 
along these two channels are similar to those along the Colorado. ALso 
there is such marked similarity between the river bluffs and the old 
lake shore line of Imperial Valley that it is impossible to tell 
where one leaves off and the other begins. The suggestion is strong 
that both river and lake terraces may have originated at approximately 
the same time, the explanation possibly being the diversion of the 
river into the Salton Basin and the formation of ancient Lake Cahuila. 

The Colorado River flows down a gently sloping delta plain, whose 
surface is inclined both toward the Salton Sea and the G\ilf of Lower 
California. The construction of this delta plain of course has been the 
prime factor in isolating the Salton Basin from the gulf, the delta 
plain having been built above sea level across the great graben to the 
Cocopa Mountains on its west side in Mexico. It is well known that 
at various times the river has discharged into the Salton Basin, which 
stands as much as 275 feet below sea level. The slope of the delta plain 
in that direction is greater than toward the gulf, hence, if the river 
broke through its bank discharging into the basin, its fall would be 
temporarily increa.sed by 275 feet, and rapid erosion would occur such 
as happened during the overflow in 1905 and 1906. Furthermore, the 
basin was then deeper than now by the amount of sediment which was 
deposited in Lake Cahuila. If the Salton Basin did not fill too rapidly, 
time might be sufficient for erosion of the Palo Verde Valley to its 
present depth and width below the Palo Verde Mesa. Climatic fluctu- 
ations which unquestionably have affected this entire region during 
the glacial stages may have been a factor in the terrace develop- 
ment. There does not seem to be evidence of elevation of the region 
which would account for the terrace development, hence the two 
factors mentioned above and possibly others have been involved in 
their development. 


Brown, J. S., Fault features of the Salton Basin, California : Jour. Geology, 
vol. 30, pp. 217-226, 1922. 

Brown, J. S., The Salton Sea region, California : U. S. Geol. Surrey Watcr- 
Supply Paper 497, 1923. 




Between the Warner Mountains and the Cascade Range far to the 
west is a high, semi-arid plateau which is part of the great volcanic 
field known as the Columbia Plateau that covers a huge area in Wash- 
ington, Oregon, and southern Idaho. Actually the Warner Mountains 
and the Hays Canyon Hange on the Nevada side were once part of this 
region, having been elevated into mountains by movements along great 
faults which broke up that section of the vast tableland in relatively 
recent geological time. Surprise Valley between the two ranges is a 
depressed block bounded by faults. 

To the California portion of the Columbia Plateau the name Modoc 
is generally given because it lies very largely within the county of that 
name, though it is also partly in Siskiyou, Shasta, and Lassen Counties. 
The elevation of the region averages about 4,500 feet above sea level, 
but there are many peaks and ridges projecting well above the general 
level. The main highway crossing the Modoc Plateau is No, 299 leading 
from Redding to Alturas, and part of No. 89 traverses the south- 
western section. A third road, which is oiled, leads from Canby on 
Highway 299 to Klamath Falls in southern Oregon. There also are a 
number of dirt roads, mostly of quite uncertain quality, but con- 
siderable areas are not reached by road. The geology of the Modoc 
country is little known, most information relating to that area con- 
cerns the vicinity of the Lava Beds National Monument. 

The most ancient features in the Modoc Plateau are hills of tuff and 
lava in the south, southeast, and north. The rocks are dominantly 
basalt whether flows or fragmental, but interlayered with them are 
various kinds of water-laid sediments. The hills form wide areas rising 
from 500 to 1,500 feet above the general plateau level, and they also 
are present as single prominent blocks .surrounded by younger forma- 
tions in Timber Mountain, Double Head, Indian Butte, and the promi- 
nent ridge bounding the west side of Tule Lake basin. Most of the 
eminences are rounded because of the great proportion of fragmental 
rocks composing them, and the long time during which they have been 
subject to weathering and erosion. In places, however, resistant rocks 
interlayered with the exploded debris form cliffs both above and below 
which are slopes, thereby evolving a terraced landscape. These volcanic 
and .sedimentary formations quite evidently are part of a once-exten- 
sive sequence which has been deeply eroded and also buried by later 
eruptions. After the volcanic cycle, probably not later than Miocene 
in age, the region was broken by faults along which there was elevation 
and depression of blocks. The slope of the layers in the visible rem- 
nants shows that the blocks were tilted to some extent in the course 
of the deformation. Because of the long time which has elapsed since 
the close of this cycle, the fault scarps have been greatly eroded and 

undoubtedly their bases have receded somewhat from the fault zones. 
The present hill fronts therefore are erosional products of land forms 
once prominently controlled by faulting. 

It is clear that this first volcanic action in the Modoc region was 
mainly explosive and was related to central openings about which 
volcanoes were constructed. The activity was interrupted on various 
occasions and, during the intervals of quiescence, sediments, mainly 
lake beds, were laid dovra. Some of these deposits were covered by 
subsequent outbursts belonging to the same cycle. 

The main part of the Modoc Plateau has been built principally in 
Pleistocene time, the oldest lavas of this sequence being definitely 
later than those of the deeply eroded Pliocene volcanoes of the adjacent 
Cascade Range. The youngest flows are so fresh that they cannot have 
been erupted more than a few centuries ago. These late volcanics are 
divisible into three groups, the oldest being by far the thickest and 
most extensive. These lavas were apparently highly liquid, forming 
thin, rather even surfaced flows, were erupted from fissures rather 
than from central openings, and flooded the region to build a plain 
of gently undulating surface. The second group is comprised of gen- 
erally much rougher surfaced flows, mostly erupted from central vents 
about which were constructed broad, low shield volcanoes. Explosive 
eruptions also occurred forming a considerable number of small 
cinder cones. 

The third group includes the most recent flows such as the Callahan 
on the northern edge of the Medicine Lake Highland, an eastward- 
projecting promontory of the Cascade Range and the Burnt Lava at 
the southern margin of the same area. The flow surfaces are chaotic 
jumbles of great blocks. Rising from their surfaces are cinder cones 
whose craters and outer slopes are almost perfectly preserved, testify- 
ing to the recency of the activity ; in fact, this suggests the definite 
possibility of further eruptions. Evidence given by the volcanics of 
the Modoc group shows that, as the cycle waned, the eruptions became 
more and more localized and more explosive. 

As the plateau was being formed by the eruption of the Modoc 
lavas, it was broken by numerous faults. The results of movements 
along the faults are conspicuously expressed in the landscape. The 
northern part of the region, especially around the basins of Lower 
Klamath, Tule, and Clear Lakes, shows a series of fault scarps trend- 
ing mostly northward. A few, however, are nearly at right angles to 
this trend. Some of the declivities are low and deeply worn, others 
are bold, steep cliffs ranging in height from 200 to more than 400 feet. 
Immediately to the west of Tule Lake basin, fresh scarps are especially 
well defined. Four of the more prominent ones can be traced for 6 to 12 




[Bull. 158 


81. Spatter cone on fairly recent basalt flow in Lava Beds National Monument, Modoc County. Cones are formed where concentrations of p;is break the crust of an 
advancing flow and throw clots of lava around the opening. In the background is a cinder cone culled Sconchin Butte. Photo hy C. \V. Vhcstcrman. 




miles north and south. Tliree of tliose scarps face eastward, one to the 
west. From the top of each cliff the plateau slopes sentlj" to the base 
of the next one. The pently inclined surfaces of the plateau blocks 
are quite flat and evidently do not depart far from the original surfaces 
of the lava flows. The fault-bounded blocks thus have rotated slightly 
about north-south axes. The boldness of some of the scarps indicates 
quite recent development. 

Rain and snow over the Modoc Plateau are relatively light and many 
of the lavas are extremely permeable, hence streams and lakes are few 
and are restricted to the extreme north and extreme south parts of 
the region, leaving the central section quite destitute of water. The 
chief rivers are the Pit, McCloud, Fall, and Lost. Old maps show 
Lost River flowing into the north end of Tule Lake, but apparentlj' 
the small volume of water which the river carries now is entirely used 
for irrigation. 

Tule Lake, once called Rhett Lake, had an area of about 150 square 
miles in 1884 ; by 1924 it had shrunk to half that size, and by 1930 was 
represented by a small, shallow pond which has since ceased to exist 
as a permanent feature. Similar recent shrinkage has taken place in 
Lower Klamath Lake which lies west of Tule Lake. Clear Lake in has been enlarged by construction of an irrigation dam. 

Lake sediments are known over considerable sections of the Modoc 
Plateau which evidently were covered by water in quite late time, 
possibly during the climax of the fourth glacial stage. Under the 
Modoc lavas are older lake beds indicating the presence of goodly 
bodies of water at still earlier times. 

It appears that toward the close of the epoch when the oldest vol- 
canic rocks in the region were erupted, probably near the end of the 
Miocene, north-trending faults developed along which blocks were 
elevated and depressed. The high areas were vigorously eroded and 
the debris accumulated in the intervening basins, being mostly de- 
posited in lakes. Later the Modoc lavas were poured out over com- 
paratively level sedimentarj' plains between the high blocks, eventually 
overwhelming some of the more deeply eroded residuals and leaving 
others as the oldest remnants in the existing landscape. In late time 
further dislocations along north-trending fractures produced the block 
structure of the present plateau and in the lower-standing areas the 
modern lakes grew. 

The rapid .shrinkage of the lakes in recent time is noteworthy. 
A small amount is the result of development of reclamation projects 
in adjacent southern Oregon, but most appears to have resulted from 
climatic change which has caused general decrease in lake size over 
this region and beyond. 

There is, however, another factor which must be considered. Tule 
Lake has no surface outlet, and, though the basin is nearly dry, there 

are no conspicuous salt deposits such as normally are left by evaporat- 
ing water in so arid a region. Therefore, water not vaporized must be 
sinking into the ground; this over a considerable period may have 
enlarged subterranean outlets by weathering and removal of rock, 
thereby increasing the loss of water. 

The Lava Beds National Monument takes in that part of the Modoc 
Plateau located near the boundary between California and Oregon, 
partl.v in Modoc County and partly in .Si,skiyou County. Comprising 
about 75 square miles, the Monument is of much historic as well as 
geologic interest. It was in this area that for half a century the fierce 
wars between the Modoc Indians and the whites went on. Under Lint- 
puash, known as Captain Jack, one of the last and bloodiest of the 
campaigns was fought. With extraordinary skill, this Indian leader 
and a small band, entrenched in stone forts, the remnants of which 
may still be seen, and in lava caves, fought a much larger force of 
white solders during 1872-73, until they were finally killed or captured. 
Mute evidence of the bitter struggle may be seen in many places about 
the monument today — battle scarred trees, splintered rock, bones of 
cattle and horses, and the stone forts which gave the beleaguered war- 
riors part of their shelter. Of course it was a losing fight, as eventually 
were all of the contests between the fewer defenders and the more 
numerous invaders. 

Bearpaw or Bearfoot Cave near the center of the Monument is about 
45 miles from Klamath Falls, Oregon, and 65 miles from Alturas, 
county seat of Modoc County in California. The paved road from 
Klamath Falls to Canby on California Highway 59 between Redding 
and Alturas passes a few miles from the Monument 's eastern boundary, 
but the only roads into the area are of dirt and not too good quality, 
for, although they are in fair condition in places, in others there are 
numerous lava boulders which make traveling slow and difficult. 

At the south end, toward Medicine Lake Highland, the elevation is 
about 5,200 feet ; but this decreases northward to about 4,140 feet at 
an old .shore line of Tule Lake which forms the northern boundary. 

The lavas of the Monument, which cover also a much more con- 
siderable area in the Modoc Plateau, radiate from faults in the 
Medicine Lake Highland to the south. One of the best views of the area 
may be obtained from a slightly eroded cinder cone which lies just 
beyond the southwest corner. On one side rises Medicine Lake Moun- 
tain ; northward is a great fanlike flow of dark lava almost free from 
vegetation. The flow has a bloeky top which is extremel.v rough. Close 
to the cone are other little explosion volcanoes with craters in 
their tops; running northward from them are dark, narrow, sinuous 
trenches. These trenches have been formed by collapse of the roofs 
of principal lava tunnels and in them are the principal caves and 
waterholes which pla}'ed so important a part in the Indian wars. 



[Bull. 158 




■ ; >" ». \ 

Fig. 82. Opening of Inva tunnel in I,ava Beds National Monument. Modoc County. The opening was furnied li.v collapse of a section of the roof. rho\o hy V. 11'. Cheaterman. 




Farther north are three long, eastward-facing, parallel oliflfs of mod- 
erate height, spaced about a mile apart. These are some of the fault 
scarps referred to in the foregoing description of the Modoc Plateau. 
At the foot of the eastern cliflF is the small remnant of the once great 
Tule Lake ; the cliff, an almost sheer precipice and therefore a quite 
recent scarp, rises about 1.000 feet; its back is smooth and slopes 
gently toward the base of the next cliff to the west. 

The most conspicuous landmarks in the area are cinder cones rising 
from 100 to 300 feet above the surface of the flows. The newer ones 
are little damaged by erosion, the older are somewhat worn ; others 
have been breached by flows that have poured from the vents. In all 
there are 11 of these little mountains, most of them lying toward the 
southern side of the Monument. 

Less conspicuous are lines of spatter cones or chimneys which mark 
the location of fissures from which lava quietly poured ; they were 
formed by small foundations of gas-rich lava thrown above the gen- 
eral level of the flow. In many of them are tubes extending downward 
for 50 feet or more, evolved by the settling of the lava column inside 
an already hardened wall of rock. Some tubes were developed by gas 
and lava spatter from holes in the roofs of advancing flows. 

Much of the lava has a smooth ropy surface, but some is broken into 
chaotic jumbles of jagged blocks. 

The lava caves and tunnels are found only in the ropy lava, and 
were formed as the roof and sides solidified leaving a cavity below 
through which the molten liquid continued to stream. The main tube 
branches so that, as the flow moved forward, little or no molten lava 
showed, it having been conducted through a sort of subway from the 
fissure to the end of the stream. Then through fractures in the sides 
or front of the flow, the lava escaped leaving the underground passage- 
ways. Because the rock jointed as it cooled and contracted, sections of 
the roofs fell in forming many short caves, hundreds of them being 
present in the Monument. In length they range from a few feet to 

several hundred feet and in height from 10 to 75 feet. The collapsed 
sections make long, narrow trenches filled with broken rock. Some of 
the tunnels are divided horizontally so that one lies above another, 
even though in the same flow. In places the roof has collapsed in such 
manner as to have sections forming natural bridges. 

Bearfoot or Bearpaw Cave in the central part of the Monument has 
several stories; the approach is a deep trench with almost vertical 
walls ; descent into it is by means of a ladder. 

From the roof of many of these tunnels hang lava stalactites, a 
testimony to the tremendous heat of the liquid stream which was able 
to melt solid rock. On the floors of a few caves are stalagmites formed 
by the drip of the molten lava from pendants in the roof. 

Because of the high porosity of the lava resulting from abundant 
joints and other openings, there are no surface streams in the Monu- 
ment ; all of the water goes underground. It is found as pools and as 
ice, for the temperature in some of these tubes is so low that water 
remains frozen even during the summer when it is verj' warm on the 
surface. In others, the ice melts during the warmer months but the 
cave temperatures are rarely more than 40°F., and the water is close 
to the freezing point all of the time. Caldwell Cave in the southeast 
corner of the Monument is one of the largest showing abundant winter 
ice which forms on the floor. In summer this is replaced by a pool of 
water. Crj-stal Cave, about 2 miles north of the one just mentioned, 
has great icicles hanging from its roof and ice stalagmites rising from 
the floor. During the summer the stalagmites and most of the pendants 
melt but some of the ice remains. 


Peacock, M. A., The Modoc lava field, north California : Geog. Review, vol. 21, 
pp. 259-275, 1931. 

Stearns, H. T.. Lava Beds National Monument, California: Geog. Soc. Phila- 
delphia, Vol. 26, pp. 239-253, 1928. 




Extending' from the north end of the Sierra Nevada virtually to the 
Canadian border is the Cascade Ran^re which is especially noted for 
the many frreat and recently active volcanoes scattered along its entire 
length. In California, the southernmost conspicuous peak is Lassen 
which erupted explosively between 1914 and 1917. From this point to 
Mount Shasta, the range is not particularly well defined though it 
does contain some cones as large as Crater Mountains (7,418 feet) 
and Burney Mountain (7.871 feet). Mount Shasta is the supreme peak 
of the range in the state standing 14,161 feet above sea level, one of 
the outstanding scenic Views in North America. North of this mighty 
eminence, the Cascade Range is better defined, being composed of a 
series of giant volcanoes which stand conspicuously above Shasta 
Valley on the west and Butte Valley on the east. Some of the vol- 
canoes, such as Miller and Eagle Rock, have been considerably eroded 
whereas others, such as Goosenest and Whaleback. are so young that 
little change has been wrought in the volcanic form. These peaks rise 
to heights of 7.000 to 8,500 feet above sea level; the cones made of 
basalt have broad gentle slopes; those formed of andesite lava are 
distinctly steeper. 

During Pliocene and early Pleistocene times in the southern high 
Cascades of California and southern Oregon, a north-trending chain 
of large, gently sloping shield volcanoes was built by outpourings of 
highly liquid basaltic lava interrupted by a few explosive inter^-als. 
The chief of these are Miller Mountain, partly buried under the later 
lavas of Willow Creek Mountain, and the Goosenest. Ball, and Rocky 
Mountains. McGavin Peak, and Secret Spring Mountain. East of these 
along Butte Valley are several contemporaneous shields which have 
been much modified b.v faulting. 

The cones were simultaneously active and there is no positive indi- 
cation of the order in which they began to grow. Miller Mountain is 
the most deeply eroded and may be the oldest whereas flows probably 
of late Pleistocene age were erupted from Ball Mountain, Ikes Peak, 
and Eagle Rock Mountain. The craters of all of these volcanoes have 
been destroyed although relics of former summit cones are on some of 
them such as Ball Mountain. None of the shields was glaciated, as were 
Mount Shasta and the great peaks of the Oregon and Washington 
sections of the Cascade Range, but the margins have been driven back 
by sapping action of springs and streams which have cut easily into 
less resistant rocks below the Cascade lavas and therefore have caused 
breakdown of the margins of the shields. 

Most of these volcanoes are elliptical in groundplan and their 
orientation suggests growth over two sets of faults, one set roughly 
north-south and the other N30°-45°W. 

Kic. M. 

Map showing distrihution of voIcan««-s in the **!lile 
Kanges. After Jtotcet M'itlianig. 




[Bull. 158 

The eastern shields never extended much beyond their present 
limits, but the larjier western ones must have been much more exten- 
sive as remnants of their lavas extend far down the Klamath River 
Valley and also into Shasta Valley. 

Mueh later than the eruptions just described are those which have 
occurred since the Shasta placiers began to retreat as the last glacial 
stage waned. There are flows and cones, some of which are so fresh 
that they have been erupted within the last thousand years or so. 

Deer Mountain (7,007 feet), for example, consists of five lava cones 
built over two nearly north-south-trending faults. Four of the cones 
are flatfish shields of basaltic lava or lava closely approaching ba.salt 
in composition. The fifth cone, the summit of the mountain, is steeper. 
No craters are visible ; they have either been destroyed by erosion or 
filled with later extrusions. Each of the five cones is heavily mantled 
with basaltic debris blown from nearby vents and all have a thin 
veneer of the pumice which was blasted from Mount Shasta in 1786. 

Near Bulani and Yellow Butte is a considerable area of flows having 
a distinct hummocky surface which at the southern end is covered by 
patches of moraines, but farther north has on top only sediment left 
by subglacial streams. It is believed that these lavas were erupted 
from fissures near the base of Mount Shasta early in the main retreat of 
the glaciers on that mountain. 

The largest of the late volcanoes north of Mount Shasta is the Whale- 
back which rises 3,000 to 4,000 feet above the adjacent lowlands. The 
mountain is a steep cone which has been modified by erosion. At the 
top there are two mounds of exploded debris ; the larger, about 500 
feet high, has a well-preserved crater in the top. 

Kegg, Soule Butte, and Ilorsethief Ranch cones are older than 
the Little Deer Mountain volcano. The first two have been largely 
destroyed by quarrying, but both evidently were composed of exploded 
debris. Ilorsethief Butte is made by two explosion cones whose adja- 
cent sides overlapped as eruptions went on. 

Little Deer Mountain is a cinder cone between 500 and 600 feet 
high breached on the south side. Surrounding it is a field of recent 
lava more than 10 square miles in area which seems to have been 
erupted during the waning stages of the volcano. 

Perhaps the most conspicuous peak in this part of the Cascade 
Range is the Goosenest, the top of which rises more than 5,000 feet 
above the end of its longest flow. The mountain was built on top of a 
much eroded shield volcano and its slopes are conspicuously steeper 
than other shields which are adjacent to it. The Goosenest is a large lava 
cone at the top of which are two cinder cones, the larger being between 
(iOO and 700 feet high, and having a well-preserved crater in the top. 
The explosive activity had almost ended before any of the visible lavas 
had been erupted, though buried streams may have been emitted as 
the outbursts were going on. 

Most of the lavas from the Goosenest volcano flowed to the west ; the 
last issued from fissures at the base of the summit cinder cone probably 
less than a thousand years ago. 

The eastern half of Shasta Valley is occupied by a great flow of 
basalt which has been called Pluto's Cave flow after the large lava 
tunnel near its southern end. This flow covers more than 50 square 
miles and exceeds 20 miles in length ; it seems to have come from 
faults close to the northeast base of Mount Shasta. Before eruption 
of this lava. Shasta Valley was a broad depression containing low hills 
of andesite .some of which still rise as islands above the later basalt. 
Almost certainly Shasta River and Parks Creek flowed through the 
valley before being diverted to their present channels by the eruption. 
The maximum thickness of this immense stream may be close to 500 
feet near Pluto's Cave but in Little Shasta Valley it decreases to a 
fews tens of feet. 

Toward the head of the flow where it is rather narrow, there is a 
prominent median ridge and over it there are oval domelike eminences 
called schoUcndomes formed by the hydrostatic pressure of the lava 
under the solid crust. In the lower part of the flow there also are 
pressure ridges and collapse depressions. 

The largest of the lava tunnels is Pluto's Cave discovered in 186:? 
which once could be traced for a mile and a half or two miles. Now 
probably half a mile is as far as it can be followed, access being easy 
in places where the roof has collapsed. Most of the accessible part of 
the tunnel has a diameter of 30 to 50 feet but in places it reaches 80 
feet. The floor is heavily covered by blocks which have fallen from 
the roof and by sand drifted in from dunes on the surface. The walls 
show that there are three and in places four superimposed flows with 
clinkery tops and bottoms, which were not separate units, but lobes 
extruded through the front of the advancing lava. 

Ova] scliollcnddmcs. a few up to 20 feet high, are scattered over the 
lower part of the flow and marginal pres-sure ridges, some with gaping 
fissures in their crests, are common along the eastern margin. Collapse 
depressions are scattered, but are most numerous near the margins of 
the lower part. Most were formed by collapse of tube roofs, but some 
are being produced today by normal weathering processes. In ground- 
plan they are elongated, circular, or irregular. Many are occupied by 
ponds and marshes. 

In the southern end of Butte Valley is a basalt flow very similar 
in character to the Pluto Cave stream, and similar basalts probably 
of the same age are extensively exposed near Bray. All seem to have 
come from fissures on the east side of the Cascade Range. A narrow 
flow of black basalt poured from a fissure located about 6,000 feet high 
on the east wall of Butte Canyon, traveled for about 10 miles, and 
ended close to Soule Ranch at an elevation of about 4,800 feet. The 
upper part is almost completely concealed by marshes and meadows 




while the lower part is buried by oiitwash of subglacial streams anil 
by exploded cinders. The best exposures are below Mount Shasta 
Woods where Hutte Creek has eroded a narrow gorfre between the 
eastern side of the flow and a glacial moraine. Most of the lava, which 
ranges from 10 to 150 feet in thickness, moved through tubes beneath a 
smooth, undulating crust. 

Another flow issued from a fissure near the top of the bold northern 
wall of Alder Creek canyon, cascaded down this declivity, and con- 
tinued for about 2 miles, ending with an abrupt front as it spread 
over the Butte Creek ba.salt. The surface features are so well preserved 
that, in spite of the forest upon it, eruptions must have occurred not 
much over a thousand years ago. 

Again within the last one or two thousand years, the Klamath River 
was blocked by basalt flows forming a lake 35 feet deeper than present 
Copco Lake at its highest level. The shore lines of this expanded lake 
are marked by conspicuous benches of diatomite above the present 
water level. Diatomite is a remarkable rock that contains myriads of 
the beautiful .shells of the minute single-celled plants called diatoms 
which live abundantly in fresh waters but more prolifically in the 
ocean. Because the shells are made of silica, a very hard substance, 
this rock if pure is quarried for use as an abrasive. 

The Copco activit.v began with the eruption of three cinder cones 
ranging from 200 to 300 feet in height ; then flows, at least nine in num- 
ber, issued from the base of the cones, the longest moving down the 
valley of the Klamath River for about 2 miles. The flow crusts are 
bloeky, but the lava beneath shows prominent columnar jointing. Most 
of the columns are vertical, but some are strongly curved like those of 
the Devil's Postpile in the Sierra Xevada. In part the curved columns 
developed where younger flows traveled along the channels in the 
older ones, while others resulted from the intrusion of a later flow 
into cracks of one already emplaced. 

Two recent flows have erupted from the sides of Shasta and 
Shastina. The older one may be seen a short distance east of Dwinnel 
Reservoir. Along its eastern side it has ridden over glacial moraines, 
but its surface is barren of glacial features, being mantled only with 
a thin veneer of cinders. The younger flow, probably the last from 
Shastina, eame from fis.sures at elevations of 9,000 to 9,500 feet and 
covered approximately 20 square miles. Highway 95 goes around its 
margin. Field evidence indicates that the Shasta glaciers had shrunk 
to about their present size before these lavas were erupted, one flood 
issuing from the end moraine of Whitney glacier only a short distance 
below the present front of the ice. These flows are quite perfectly 
preserveii, have very steep fronts, and little forest cover, all testimony 
of their extreme youth. 

From the preceding account it is evident that this remarkable area 
ill comparatively recent time was one of the world's great volcanic 

fields. The frecpient eruptions must have been magnificent spectacles 
comparable to those which men have witnessed at many volcanic areas 
round about the world. The recency of many of the lavas strongly 
suggests dormancy rather than extinction for parts of the area at least. 

Older volcanic features also are present, but are much spec- 
tacular. For example, six volcanic necks which once served as feeders 
for flows stand close to the Klamath River near Copco Dam, and there 
are various others in the same area. Some are found in Shasta Valley. 

On the eastern side of the Cascade Range and .separating it from 
the Klamath Mountains to the west is Shasta Valley, a roughly oval 
basin measuring about 30 miles north-south and 15 miles 
Most of it stands between 2,400 and 2,800 feet above sea level, hence 
the Cascade Range rises very conspicuously above it. The eastern half 
of the valley is occupied by a huge flow recently erupted from the 
side of Mount Shasta, while the western part consists of older vol- 
canics which have been eroded into a multitude of hills ranging in 
height from a few feet to 200 and rarely 300 feet. Most of these hills 
are domes or cones, but some are mesas or ridges. They look much like 
little cinder cones of fairly recent origin, but actually they are older 
lavas which have been deeply eroded. Between the hills lie small ponds 
and marshes and the alluvial flats of winding streams, chief of which 
are Shasta River and its tributary Parks Creek. In the northern half 
of Shasta Valley, there are few streams because of the porous char- 
acter of the lavas and most of the underground water empties into 
the ponds and meadows of the lower southern end. 

On the east side of the Cascade Range is Butte Valley, the bed of 
an ancient lake, standing approximately 4,200 feet above sea level. 
Meiss Lake is all that remains of a former much larger bodyof water 
that drained through Sam's Neck into the Klamath River. As with 
Shasta Valley, this depression is a large structural basin, but the faults 
which bound it are much younger than those margining the western 
basin. Several flat-floored grabenslike Sam's Neck and Pleasant Valley 
extend beyond the margin of the basin between elevated fault blocks. 

AVhen the last glaciers on Mount Shasta reached their maximum 
about 25.000 or more years ago, those descending its northwest slopes 
spread into Shasta Valley leaving end moraines along the shores of 
present Dwinnel Reservoir and recessional barriers .southward as far 
as the towni of Weed. Today these glaciers have been reduced to a 
length of about 2 miles and none descend below 10,000 feet. A large 
glacier starting at about 7.000 feet flowed down the canyons of Alder 
and Butte Creeks reachitig an elevation of about 4.800 feet near Soule 
Ranch. It overflowed the western rim of the canyon near Granada 
Ranch, though its thickness was only 400 or 500 feet, and crossed the 
opposite rim near Mount Sha.sta Woods, leaving huge lateral moraines. 
Beyond the ends of the glaciers much outwash was deposited by the 
streams flowing from them. 



I Bull. 158 



^r«> Butte Flb4-D«(nfl> 

Ciodcr Conr I 

Cinder Con«. , 

fBd»«lI>c 3*i.at4-vstca>)ef 

Kic. S4. !*iinririinii(' skptrh r.f Mcnnl Sli;is);i ;inil vicinity in the California section of tjie Cascadi' Uuhri^s. After Iloirel W'illintfis. 

Mount Shasta 

Mount Shasta is one of the most spectacular of a great galaxy of 
volcanoes scattered along the Cascade Mountains from Lassen Peak 
on the south to Mount Baker 500 miles northward in Washington. 
Shasta is an isolated mountain rising about 10,000 feet above its base 
and 14,161 feet above sea level. In majesty and beauty it is exceeded 
among the Cascade volcanoes only by the higher Mount Rainier, prime 
feature of the National Park of that name in Washington, but others 
like Hood in Oregon, Baker. St. Helens, and Glacier Peak in Wash- 
ington are superb structures, standing like great temples above their 

How old Shasta is we cannot determine, but there are suggestions 
that the first eruptions began toward the close of Pliocene time. The 
latest products certainly are not more than a few hundred years old 
and a hot spring near the summit may indicate that fresh lava still 
exists beneath the mountain. 

Shasta, while not the highest of the Cascade volcanoes, probably is 
the largest, for it rises from surroundings about 4,500 feet above sea 
level while Mount Rainier is built on an elevated platform whose sur- 
face stands about 8.000 feet above the sea. Some hold that there has 
been considerable erosion from the top of Rainier, even as much as 
2,000 feet of the top being gone, while the summit of Shasta probably 
has not been lowered more than 200 or 300 feet. Even if removal from 
Rainier is as great as indicated above, the Shasta cone exceeds it in 
bulk and height. 

Viewed from the east, Shasta appears to be a single mountain, but 
from other positions it has the form of a double cone, for a small vol- 
cano, Shastina, rises boldly from its western side. Shasta, like many 
volcanic giants similarly constructed, has rather gentle slopes near 
the base while its upper part becomes increasingly steep. This slope 
change is caused primarily by the difference in fluidity of the earlier 
and later lavas ; the later lavas being much more sticky when erupted 
than were the earlier formed shorter, thicker flows which piled up 
around the central vent making terraces ending in steep, high steps. 
Furthermore river and glacial action have added their effects, for 
above 8,000 feet there has been deep erosion while below 5,000 feet 

much deposition by streams, gravity streaming, and glaciers has aided 
in reducing the slope. 

Besides the two main cones, there is a line of small cinder cones 
and plug domes located along a north-south fracture traversing the 
summit of Shasta and a very prominent plug dome. Black Butte, 
which rises more than 2,500 feet above the western base of the moun- 
tain. Lava flows of rather late date have been erupted along the base 
of the volcano. 

The lower 5,000 feet of Shasta are mantled with thick brush, while 
between 5,000 and 8,000 feet there is a belt of dense pine and fir forest 
which gradually merges into the treeless alpine top of the mountain. 
This alpine section is normally clad with snow from October to June 
and this greatly enhances the beauty of the peak. Five valley glaciers 
are fed from as many valley heads in the treeless upper reaches, the 
largest of these ice tongues being located on the northern side of the 
mountain where they descend to about 9.000 feet. 

Although the main volcano appears to be deeply scarred by erosion, 
actually it has been marred very little for the deepest canyon, that 
of Mud Creek, cuts only 1,500 feet into it. Thus a small part of the 
structure of the cone is visible. That part is composed very largely 
of lava flows, layers of exploded fragments being relatively few. Of the 
latter, the most abundant exposures are in the walls of Mud Creek 
canyon. The last explosions of Shasta came from the summit vent and 
produced the Red Banks, a deposit of pumice mantling the cirque heads 
on the south side of the peak. 

The crater of the volcano lies beneath a snowfieUl about 200 yards 
across. At the margin of the snowfield is a small hot spring. 

Evidence indicates that all but the latest blocky lava flows on the 
northeast side of Shasta and the final deposits of pumice had been 
erupted when a north-south fracture broke through the summit of the 
volcano. No displacement of the surface shows along the fissure and 
little or none may have occurred, but its direction is clearly indicated 
by the linear arrangement of five plug domes, two cinder cones, and 
one lava cone. The largest dome is Gray Butte, about 4 miles south 
of Shasta, which rises about 1,500 feet above its surroundings; the 




i IG. S». Mt. Shust:i and iihaata Valiv;. . Thv LiUi lu il.t- lorii:ruuiii] are croiiej reUiuaiUs of old la\a llowS. Photo courtesy Faircftild Aerial Surreyx. 



(Bull. 158 


Fio. 8C. Mt. Shasta, a composite volcano composed of two cones. The higher cone, Shasta, is older and has been deepl.v eroded b.v streams and Rlaciers ; the lower cone, 
Shastina. is younger and is less eroded. Skctcheil from a photograph by It. ,V. U'AecIer. .Voiman E. A. Jlinds, (lEOMOKf'IlOI.OGY (copyright IHiS by Prenticc-llall. Inc., 
.Vew- York), lieprodaccd by permission of the publisher. 





Kio. 87. Mt. Shasta and Shastinn, showinR the Rreat sash in the crater and side probably caused by eiplosion. Photo courlejy L'. S. Armg Air Corps. 



[Bull. 158 

^•'■.'.'■;?^v V- 


Fig. SS. Sketch of Shnst.T Dam on the Sncramento River about 16 miles north of KeddiriK- Courtesy V. S. Itureau of Jyclamalion. 




length of this dome is nearly 2 miles, but the rock core beneath may 
not be more than half that, the remainder being the great covering of 
talus blocks. The cinder cones are small, the northern being only 200 
feet higli and the southern 800 feet ; their summits have been smoothed 
and the craters destroyed by glacial action. At the south end of the 
fissure about 2 miles from the town of McCloud is Bear Butte, a small, 
steep-sided hill composed of dark lava. 

A view of Shasta from the west shows a broad low cone rising from 
its long southern slope. This appears to be a miniature shield volcano 
of the Hawaiian type, surmounted by remnants of a cinder cone. The 
lavas composing the main part of this volcano were very liquid when 
erupted and spread over a wide area even though the slopes they 
traversed were quite gentle. Most of the flows went southward, though 
one was partly diverted to the north and changed the course of 
Panther Creek, Others traveled eastward and encircled Bear Butte, 
the small lava cone previously described. The longest outpourings 
from the shield volcano descended the canyon of the Sacramento 
River for more than 40 miles as long, narrow tongues. The river has 
cut through the flows, exposing in some places gravels that lay in the 
bottom of the canyon when the lava invaded and in others the bedrock 
into which the Sacramento had cut its canyon. Excellent sections of 
these flows may be seen at Shasta Springs where Mossbrae Palls pours 
out in great volume much of the underground water coming from 
Mount Shasta and at other places farther down the canj'on. This water 
is hea\'ily charged with mineral salts. 

The main cone of Shasta seems to have attained its present elevation 
before the large minor cone. Shastina, began to form. It is possible 
that an east-west fissure developed about the same time as the north- 
south one earlier described, the two intersecting at the top of the 
volcano. The first eruptions along this east-west fracture built a small 
cone about a mile and a half west of the summit of Shasta and some- 
what later Shastina began at a second vent a half mile farther west. 
Until late in its history, Shastina was constructed from short, quite 
viscous flows which issued from a single vent, but the last principal 
eruptions came from fissures which opened on the west side of the cone. 

The almost perfectly preser\-ed summit crater of Shastina is a 
bowl-shaped depression about .300 feet deep and half a mile in diameter. 
Within it are two more or less conical mounds which may be plug 
domes with much broken tops. In the western side of the crater is a 
deep breach and below this lies a huge V-shaped gash; possibly both 
of these features resulted from violent downward directed explosions 
accompanying the elevation of the domes within the crater, a not 
uncommon feature at volcanic mountains. 

Later explosive eruptions occurred at lower elevations, most of them 
centering about 3,000 feet below the rim of the Shastina crater, though 

activity progressed westward so that some occurred 7,000 feet below 
or at an elevation of about 5,000 feet above sea level. Dark flows of 
blocky lava also poured from the fissures covering a considerable area ; 
the longest descended almost to the present site of the town of Weed 
on Highway 99. These recent flows cannot be more than 200 years old. 

Rising conspicuously near Highway 99 not far from the town of 
Weed is the prominent eminence known as Black Butte whose summit 
stands about 2,500 feet above its surroundings. From some places the 
Butte appears to be an almost perfectly conical mountain, but else- 
where this form is seen to be modified bj- a series of arcuate ridges 
from 200 to 1.000 feet below the top and located on the northwest side. 
The diameter of Black Butte is about a mile and a half. The whole of it 
appears to be made of great blocks of lava which become larger toward 
the top, only a few crags of coherent rock being visible. 

The common belief is that this mountain is a volcano like Cinder 
Cone of Lassen Park and various others, but actually it is a plug 
dome very heavily mantled with talus. The core may be cylindrical in 
form with a diameter of little less than a mile. As the mass rose, cool- 
ing and contracting, it was heavily fractured and the great banks of 
talus formed. Field e'S'idence shows that prior to the protrusion of this 
dome, explosive eruptions occurred, but whether a small cone was built 
has not been determined. Black Butte is one of the latest products of 
Shastan activity and its completion very likely took place in a few 
years, a striking contrast with the many thousands of years required 
for the building of Shasta. 

Glaciers today cover a very small area on Mount Shasta, about 3 
square miles, whereas not far back in Pleistocene time ice apparently 
blanketed the entire peak. Of the valley glaciers, the Hotlum on the 
northeastern side is by far the largest, accounting for almost half the 
total extent of the ice. Bolam and Whitney to the west of Hotlum and 
Konwakiton on the south side of the mountain are the others. Hotlum 
glacier descends to an elevation of about 9,000 feet, the lowest point 
reached by any of the ice tongues ; in the early days of exploring Mount 
Shasta, this ice mass was thought to be about 2,500 feet thick, but now 
we know that actually it measures only 300 feet which is a maximum 
for any on the peak. Konwakiton, also known as Mud Creek glacier, 
has been especially conspicuous at times because of the great mud 
flows which have descended from it. A few tens of years ago. this 
glacier was about 5 miles long but since there has been considerable 
recession. Near its head, the slope of the ice is steep, while farther 
down, it flattens out, the glacier ending on the brink of a cliff in Mud 
Creek Canyon. During dry seasons, the run-off from melting snow, 
which in wetter years is more gradual and sinks into the ground, 
becomes torrential. Great streams find their way down the crevasses 
in the ice and emerge on the floor of the valley at the end of the glacier. 




[Bull. 158 

The water, carr>-ing large blocks of ice broken from the snout of the 
glacier, races through a narrow canyon, undermining the weak walls 
made of tuff and breccia. At times part of the undercut eastern wall 
collapses into the bottom of the gorge forming temporary dams. Rather 
quickly sufficient water is impounded behind the barrier either to flow 
over it or to break through and sweep it on down the canyon. This 
debris-laden flood after following the canyon for about 6 miles comes 
out onto flatter land, spills over the banks of the stream, and spreads 
thick sheets of sand and mud in which are embedded great boulders. 
Much of the finer detritus is carried into the McCloud River, from 
there into the Pit, and finally into the Sacramento, at times rendering 
that stream turbid for 200 miles below the junction with the Pit. 
These great mud flows were particularly well illustrated during the 
dry seasons of 1924, 1926, and 1931. 

Below Wintun and Hotlum glaciers, other mud flows may be seen, 
particularly along the banks of Inconstance Creek, but much of the 
canyons which these tongues follow is cut in lava flows and therefore 
less debris is available. 

Evidence of the fairly late coverage of the entire volcano by ice is 
provided by the abundance of morainal deposits around the base. 
However, the glacial history is not well enough known to determine 
whether there were various stages, though very Likely such was the 
case as may be inferred from their existence farther north in the 
Cascade Mountains of Oregon, in the nearby Klamath Mountains, and 
in the Sierra Nevada. 

When the glaciers reached their maximum, they descended into 
Shasta Valley west of the peak, crossed it, and rose to a height of about 
4,000 feet along the mountain slopes on the western side. On the south- 
west, the ice covered Quail Mountain and probably was joined by 
other glaciers coming eastward from the Klamath Mountains. In the 
principal valley on the north side of Mount Shasta, the ice was prob- 
ably at least 1,000 feet thick, while on the south it rose within 100 feet 
of the top of Red Butte as is proved by polished and striated rock. 
All but the highest points of Gray Butte were overwhelmed, as were 
the cinder cones, lava domes, shield volcano, and probably Bear Butte 
farther south. 

Especially fine glacial features are the great cirques on the south- 
west side of Mount Shasta and some of lesser magnitude on the east. 
The most perfect of the lot is that at the head of Cascade Gulch between 
Shasta and Shastina. There are well-preserved moraines in the cirque. 
Elsewhere high on the mountain good moraines are scarce except at the 
ends of existing glaciers, but there are some examples on the plateau 
southwest of Horse Camp. The road to the town of McCloud along the 
south base of the mountain cuts through a group of side moraines, 
while in the canyons of Whitney and Bolam Creeks these deposits lie 
beneath recent flows of blocky lava. 

In spite of the abundance of snow and ice on Mount Shasta, there 
are few large streams and these cease to flow during the winter; most 
of them are restricted to the north and east sides of the mountain. 
The cause of the scarcity of water is the porosity of the lavas and the 
glacial debris. The water sinks below the surface flowing underground 
to the base of the cone where it comes out in many good sized springs, 
notably on the south and southwest sides. The finest display is at 
Mossbrae Palls in the Sacramento Canyon. 

Traces of avalanches are numerous especially at elevations of about 
8,000 feet where the steep upper slopes gradually flatten out toward 
the mouths of cirques. Frost wedging apparently dislodges large 
masses from the highest ridges ; in some cases they race over snow- 
banks increasing in volume as they go. One by the side of the trail up 
Mount Shasta near Horse Camp, occurring probably not more than 
50 or 60 years ago, plowed a path half a mile long through tall timber. 

Fio. 89. Flow of basalt that descended the upper part of the Sacramento Canyon 
for about 40 miles from a vent on the lower, southern slope of Mt. Shasta. The Sac- 
ramento River has cut through the flow into much older rocks of the underlying 
formations. Photo by Olaf P. Jenkins. 

Pliocene (?) Cascade Volcanoes 

Between the Mount Shasta and the Medicine Lake Highland is a 
broad, irregular mountainous belt whose lavas appear at a few places 
under the volcanic rocks near the middle of the Highland. Their 
principal display is an arcuate outcrop around its eastern margin 
from which they extend westward and merge into the base of Mount 




This area is composcil principally of massive, deeply eroded, j;ray isli, 
loose-textured lavas, most of wliieli are andesites and basalts whieh 
appear to have been erupted from volcanoes of the Shasta type. In fact 
the character of the rocks and the topo<;raphy they produce definitely 
relate them to that sort of volcano, hence they are co itrasted with the 
oldest lavas of the nearby Modoc Plateau which are darker in color 
and were poured out as fissure flows. 

The relief of the area occupied by this belt of frray lavas reaches a 
maximum of 6,000 feet. Haijrht Jlountain, near the western margin 
exceeds 8,000 feet; Garner Mountain and Horse Peak each are more 
than 7,000 feet. Grizzly Peak and several other conspicuous summits 
stand over 6,000 feet. On the other hand, the Pit River, which crosses 
the southern part of the area, has cut a gorge below the 2,000-foot 
mark into the lavas. 

Most of the landscape is the product of erosion, being determined 
by the Pit and McCloud rivers together with their tributaries. How- 
ever, the major forms seem to be dependent upon original peaks which 
had been developed during a considerable volcanic cycle. These heights 
are deeply eroded conical or pyramidal mountains so similar in form 
to Mount Shasta itself that they are far more likely the eroded products 
of like volcanoes than dissected remnants of a lava plateau. 

The lavas weather easily and have produced a thick soil which sup- 
ports a hea\"j' forest growth ; this results in scarcity of outcrops of 
fresh rock and makes study of the area a matter of much difficulty. 

The volcanoes from which these gray lavas were erupted are believed 
to have been active in Pliocene time, though the evidence is rather 

Medicine Lake Highland 

About 35 miles east of Mount Shasta and somewhat to the south of 
the Lava Beds National Monument is the Medicine Lake Highland, a 
volcanic center roughly 20 miles in diameter which marks the eastern 
boundary of the Cascade Range in this section of California. On the 
north, east, and south, the highland is surrounded by the undulating 
surface of the Modoc Lava Plateau which in part is broken into small, 
fault block mountains. 

The highland is described as "converging upward to a roughly 
elliptical rampart of cones and domes," 4 by 6 miles across, on which 
the highest point is Mount Hoffman, 7,928 feet. This rampart enclosed 
an elongated basin, the western side of which is occupied by shallow 
Medicine liake whose surface stands about 6,500 feet above sea level. 
The lake has no outlet, but its water is fresh probably because of 
sufficient seepage into the rocks below to prevent concentration of 
salts brought into it by feeding streams. 

The basement rocks of the highland are basaltic and andesitic lavas 
like those of the Modoc Plateau immediately adjacent. The growth of 
the Medicine Lake eminence was started by eruption of rather fluid 

andesitic lavas which built a broad sliield volcano about 20 miles in 
diameter. It is believed that the central part of the shiehi later col- 
lapsed forming a basin or caldcra about 6 miles long and 4 miles in 
width. As this was going on, more viscous lava was forced up along 
the fractures forming rim volcanoes. Eruptions continued pouring 
lava into the caldcra until the cones were high enough to discharge 
flows down the side of the original shield volcano. As a result the 
fractures were .sealed, the walls of the caldera were hidden, and the 
basin was surrounded by the rampart of cones. 

Fio. 90. Panoramic sketch from the top of Medicine Mountain, showing part 
of the elliptical rampart enclosing Medicine Lake basin. 1, Recent lava flow between 
Medicine Lake and the northern ridge; 2, Mt. Hoffman; 3, Glass Mountain. After 
C. A. Anderson. 

New vents then opened giving forth sticky, lighter colored lavas 
of composition similar to or approaching that of granite. The floor of 
the summit basin is partly covered by a quite recent flow of this t>-pe. 
During this late cycle, more openings were developed on the lower 
flanks of the old shield volcano, flooding all but the western side with 
flows of basalt. Many small cinder cones also were formed by mild 
explosions. On the southeastern side of the shield, a number of cinder 
cones have coalesced to form a broad ridge. The Modoc Lava Beds are 
the northermost expression of the basaltic flows discharged from the 
fissures along that flank of the Medicine Lake shield volcano. ■ 

Recent faulting has developed small scarps and some of the recent 
volcanic activity has centered along these fractures forming cinder 
cones and lava cones. 

The number of small cinder cones scattered over the highland 
exceeds a hundred and the latest of them probably have been formed 
within the last 500 years. 

The last basalt flows are very differently distributed for none of 
them are present in the summit basin or the elliptical rampart sur- 
rounding it, AU came from vents on the northern, eastern, and south- 
ern sides of the shield volcano mostly located between 5,000 and 6.000 
feet above sea level. Soils are poorly developed, showing the recency 
of the eruptions which probably ranged from culmination of the last 
glacial stage to the last few centuries. 

Flows of composition approaching that of granite are limited with 
exception of those of Little Glass Mountain on the west side to the 



[Bull. 158 

center and the rampart of Medicine Lake Highland ; some are partly 
glassy while others are obsidian, the latter representing some of the 
most recent eruptions in this area. In addition there was considerable 
explosive eruption of pumice. At both Glass Mountain and Little Glass 
Mountain, the volcanic cycle was initiated by outbursts of pumice 
which built up steep sided cones, while later much obsidian was erupted 
at both volcanoes. Pumice and obsidian also were erupted at still other 

Lassen Volcanic National Park 

Very close to the soutliern end of the Cascade Mountains where 
they adjoin the Sierra Nevada lies a most interesting area which has 
been set apart as Lassen Volcanic National Park. The best approach is 
Highway 47 which goes from Red Bluff in the Sacramento Valley to 
Mineral and Chester and eventually across the Sierra Nevada. At 
Mineral a road turns north which gives the traveler a splendid view of 

Fig. 91. Cross-section illustrating the origin of Medicine Lake caltlera and rim 
volcanoes, a, Shield volcano made of flows of andesite lava. 6, Collapse of central 
block along faults. Lava was squeezed up along fractures and poured out on caldera 
floor. Solid black area is lava chamber, c, Continued growth of rim volcanoes dis- 
charging lavas down outer slopes of original shield volcano as well as into caldera. 
d, Cross section of present highland showing basaltic cinder cones (stippled) and 
basalt flows (vertical lines) on outer flanks of shield volcano. Black area in central 
basin is a recent lava flow. After C. A. Anderaon. 

the principal scenic features of the Lassen Park. Highway 47 from 
Redding and 37, taking off from the Redding-Alturas road (No. 299) 
about 5 miles east of Burney, enter the Park at Manzanita Lake on 
the north side. Unpaved roads lead from immediately west of Chester 
and reach sections of the park not accessible by the paved highway; 
one goes up Warner Valley into a region of hot springs, including the 




,v ■ 

Ku;. '.<2. rain.raiu;i ..1 I.illle G;a>.- .M..uTit;.iii. Si^ki.\...u r...uii(.i . ^l...»illK twu tlaws. uf rbyolite .-.el.... ..:. .. .... ;: L in c'ntr:il p:irt of pholi.sraph. Pressure 

ridges that developed as flow advanced show on left side. White bill in background is a cinder cone older than the flows. Kocks surrounding flow are older basalt of the 
Modoc Plateau. Photo by C. W. Cheaterman. 

Geysers, Boiling Lake, and the Devil 's Kitchen, centered near Drakes- 
bad, the seeond passes along the eastern side of Harkness Volcano to 
Juniper Lake. Features to be seen along the principal highway 
through Lassen Park are many. This road leads through Mill Valley, 
across the ancient, much faulted crater of Brokeoff Volcano which is 
dotted with hot springs. Then, after passing close to the fumaroles 
(hot gas springs) and boiling springs of Bumpass Hell and glacial 
lakes Emerald and Helen, it ascends the southeast shoulder of Lassen 
Peak, where good views of the manj- volcanic domes, principal features 
of the Park, and of earlier flows from the original Lassen crater may 
be obtained. Following the upper part of Kings Creek Valley, the 
highway goes around the side of bold, talus-mantled White Mountain, 

and crosses the valleys of Hat and Lost creeks where the mud-flows 
of 1915 caused much devastation. 

The Lassen region for a long time has been a center of volcanic 
action, older lavas and explosion products showing at many places. 
As one phase of this activity, a great volcano was built in the southwest 
corner of the Park, eventually reaching a height of about 11.000 feet 
above sea level and a diameter of about 15 miles. Since its completion, 
this cone has been so much destroyed by faulting and erosion that it is 
appropriately known as Jlount Brokeoff. In the later history of the 
construction of the Brokeoff Volcano, there also occurred the building 
of four shield volcanoes of Hawaiian type, one situated at each corner 
of the Central Plateau of the Park; these are Raker and Prospect 



[Bull. 158 

peaks, Red Mountain and Mount Harkness. Each of these mountains 
is surmounted by well-preserved explosion or cinder cones which rise 
within the more or less nearly circular fault basins called calderas at 
the tops of the mountains. 

Fig. 93. Section across the BrokeofF Volcano showing by dashed line the approxi- 
mate original form. Present surface is indicated by solid line. The top of the moun- 
tain collapsed ulonp faults, producing caldera in the top. The Boy Scout Hills are 
plug domes erupted through conduits opened in the lower southern flank of the vol- 
cano. After Hoicel Williams. 

The eruption of Red Mountain had ceased when an irregular body 
of rhyolite was intruded into the cone at its northern base. Also after 
the completion of Raker Peak, a steep-sided dome of lava was pro- 
truded through its southern flank. About the same time, a new orifice 
opened on the northeast slope of the Brokeoff volcano, probably close 
to if not immediately beneath the present Lassen Peak. Prom this 
crater streams of fluid lava flowed radially though principally to the 
north piling up to a greatest thickness of 1,.500 feet. These flows are 
the black, glassy, beautifully columnar streams that completely 
encircle the base of Lassen Peak. 

Lassen Peak represents a crater filling of the volcano just described. 
Gas-rich lava had poured out as flows making the mountain just 
described. Then partly solid, partly liquid gas-poor lava rose to form 
the Lassen volcanic dome ; its sides were abraded as they ground 
against the walls of the vent and its surface broke apart into blocks 
which slid down the slopes forming great piles of talus. 

Smaller domes rose to the south of Lassen Peak forming Bumpass 
Mountain, Mount Helen, Eagle Peak, and Vulcan's Castle, and some 
of these were connected by short, thick flows of evidently sticky lava. 
Possibly at about the same time the domes forming Morgan and Boy 
Scout Ilills were forced through the southern base of the Brokeoff 
volcano and that of Wlaite Mountain was elevated through vents from 
which lavas had been poured long before. The domes that border 
Lost Creek may also belong to this episode. It is evident that all of the 
domes were rapidly constructed as compared with the much slower 
building of the older volcanoes from layers of lava and exploded 

This phase of the volcanic action was followed by the collapse of 
the summit of Mount Brokeoff along a series of nearly vertical faults 

producing a caldera having an area of about 2} square miles. Its origin 
is similar to tliat of the Crater Lake Basin in Oregon and many other 
basins in volcanic mountains. The cause of collapse may have been 
the large amount of withdrawal of lava from below the area in the 
formation of the domes above described though very likely under- 
ground migration of lava also played a part. 

Lassen Peak appears to have risen to about its present height when 
a vent. Crescent Crater, opened on its northeastern side and erupted 
flows of lava. Then, about 200 years ago, a line of cones developed at 
the northwest base of Lassen throwing out clouds of tuff and pumice. 
Two rather cylindrical domes of highly viscous lava were elevated 
through these cones to form the Chaos Crags. The latter and northern 
of the two domes had risen about 1,800 feet when steam explosions 
burst from its northern base causing that side to collapse and sending 
a great avalanche of angular blocks over about 2i square miles imme- 
diately adjacent forming the wilderness of boulders called Chaos 

In the northeastern part of Lassen Park is Cinder Cone, a finely 
preserved, very young explosion cone built perhaps about 500 A.D. 
Not only was the cone formed by the explosions, but the area round- 
about, more than 30 square miles in extent, was mantled with the 



v.c. PP !•? cp 

KlG. tl-t. View north from Hnik.'uff .Mi.unkiiii :nruss Ihi- di)\vnf:a]lti'.i i':ildiTn 
to Mt. Oilier (M.D.) and Pilot Pinnacle (P.P.). Jl.L.C.. Blue Lake Canyon: I.o.l:, 
Loonii-! Peak ; C.C., Chaos Crags ; V.C. Vulcan's Casllc : L.l'., Las.seu Peak ; K.I'.. 
Eagle Peak. Dark Tongue on Lassen Peak is the 1915 lava flow. After llotcel 




I^assen IVak. Las»en Volcanic National Park, durini; an artificial eruption, part of the cpremony of (lp<licatinn of the park. Masses of the solid rock of this 
iniee volcanic dome show through the great banks of talus which mantle its side. Fhoto vourlexy V . S. Army Air Corps. 



[Bull. 158 

Fio. 96. 

Xorth-south cross section through Lassen Peak, Lassen Volcanic 
National Park. After Ilotcel Williams. 

debris. Cinder Cone is almost undamaged by erosion and has a per- 
fectly preserved crater in the top. The layered structure of the little 
mountain, representing the deposits of the various explosions, can be 
seen in the crater walls. Round about the base are many of the larger 
fragments hurled from the vent, some of them measuring 4 and 5 feet 
in diameter. At a later time flows of basalt were erupted from frac- 
tures at the base of the mountain, and then these were partly covered 
by exploded fragments. Finally two very late flows appeared, the 
second quite reliably dated about 1851. 

As late as 1857 steam rose from the domes of Chaos Crags. In May, 
1914, Lassen Peak became active, and, for a year, explosions occurred 
at irregular intervals. In May, 1915, lava rose in the summit crater 
spilling over the rim on its northeast and northwest sides, melting 
snow and causing extensive mudflows. On the 22nd of the same month, 
a horizontally directed blast was loosed from the northeast side of the 
crater, causing more damage along the headwaters of Hat and Lost 
Creeks. Afterward the activity became less vigorous and died out in 
the summer of 1917 with no later recurrence. 

The Lassen Dome is by far the largest and highest of these curious 
but common volcanic features in Lassen Park ; it rises about 3,000 
feet above its surroundings, standing conspicuously above the smaller 
domes on its south and northwest sides. The mountain has the form 
of a truncated pyramid. The steep-sided solid rock core probably 
mea.sures about a square mile in extent, but enormous masses of talus 
spread out from it and cover at least twice that much acreage. Espe- 
cially on the south and east flanks, high rugged crags of the core stand 
out. but in most places the mantle of debris completely covers it. The 
great boulder banks were almost entirely developed by the fracturing 
of the core as it rose, cooled, and contracted, for hot rock shrinks in 
volume as it cools. 

The activity which started in 1914 materially changed the form of 
the .summit crater which before had been a smooth bowl about 360 feet 
in maximum depth and floored with volcanic sand. No fumaroles (hot 
pas springs) or other signs of activity were known within the memory 
of those living nearby. Snow commonly accumulated to depths of at 

least 40 feet within the crater. The new volcanic cj'cle commenced on 
May 30, 1914, with a short, mild explosion. During the first year more 
than 150 other outbursts took place enlarging the crater to a diameter 
of about 1,000 feet. During 1914-15, snow accumulation on Lassen 
Peak was unusually heavy and this may have been responsible for the 
activity of 1915 as the meltwater seeped into the earth and came in 
contact with hot lava. Between May 16 and 18 a of black lava 
rose in the notch in the western part of the crater rim and on the 19th 
spilled out in the form of a tongue about 1,000 feet long. What hap- 
pened on the eastern side of the mountain during this time is not 
clear, but on May 19 a devastating mud flow poured down Ilat and 
Lost Creek valleys carrying 20-ton boulders for a distance of 5 or 6 
miles. Three days later a second mud flow occurred in the same place 
with minor ones of similar sort on the north and west sides of the 
mountain. At the same time on the eastern side there came a terrific 
horizontal blast which felled trees for miles around so that their trunks 
were aligned in the direction of the onrushing cloud of gas and rock 
fragments. Clouds of steam and ash rose vertically above the crater 
to a height of more than 5 miles. 

Following the vigorous activity of 1915, the energy of the volcano 
seems to have been largely exhausted. Explosions continued for 2 
years at irregular intervals, culminating in violent outbursts of May 
and June, 1917. There had been considerable snow during the jirevious 
winter and this apparently made more underground water available 
to be turned into steam. After 1917 no eruptions have occurred. The 
principal effect of the explosions of the two years was to still 
further modify the form of the crater. The temperatures generated 
during the 1914-17 cycle and the type of explosions indicate that 
Lassen is a waning volcano far on the road to complete extinction. 

The volcanic domes called Chaos Crags and the huge avalanche 
deposit named Chaos Jumbles are the most startling features of Lassen 
Park outside of Lassen Peak itself. It appears that before the domes 
were elevated, a north-south fissure probably opened at the northern 
base of Lassen Peak and explosion cones were built along it. Only part 
of one cone now shows, but evidence indicates that there were at least 
two others. The exploded fragments cover a modest area, but bombs 
and fragments up to 3 feet in length are found at least 3 miles from the 
cones while abundant bombs 6 feet long are embedded in the deposits 
2 miles away. Probably not more than a few weeks or months after the 
formation of the cones, two great domes were protruded in the cone 
area. Each was about a mile in diameter at the base and the northern 
one rose 1,800 feet above its surroundings. Huge banks of talus com- 
posed of angular blocks blanket the sides of the domes and many of 
them are 1,000 feet high. Through the talus and above it rise ragged 
pinnacles and peaks of more solid rock. 




Fio. 97. Kind's Falls in I^as-sen Volcanic National Park. Many lava flows con- 
tain oiten .'ipjices into which water readily sinks. Where valleys are cut into the lava. 
Iari;e, tx'autiful waterfalls may develop. Photo courtety ire»(ern Pacific Railroad. 

The later northern dome was made of greatly fractured rock and 
much of it rested on the loose exploded frafrments of the cone beneath, 
a most perilous setting. Finally explosions occurred at the base of this 
dome hurling an enormous quantity of huge blocks out to the north. 
The tremendous speed at which this avalanche traveled can be judged 
from the fact that its momentum carried the blocks 400 feet up the 
slope of Table Mountain 2 miles away wliere Chaos Jumbles ends with 
a precipitous front. The sharpness of the boundaries of the avalanche 
mass is notable for almost everywhere its margins are steep moxinds, 
in places more than 100 feet high. It is believed that the bla-sts which 
destroj-ed tliis part of the dome did not occur more than 200 years ago. 

The explosive activity at Cinder Cone in the northeast corner of 
Lassen Park formed a volcano about half a mile across at the base and 
600 feet high. The cone was not formed during a single cycle of 
activity as are many such mountains, as is proved by the presence 
of two crater rims, and there are two other rim remnants on the north- 
west side of the cone. Furthermore remnants of small cones are present 
on the southwest side of tlie main mountain. Thus it is evident that 
activity continued over a considerable period possibly with interrup- 
tions of various lengths between the minor cycles. Then followed the 
eruption of a basaltic lava flow from the south base of the cone and 
further explosions which partly mantled the flow. Later two or more 
flows poured out, the youngest of whicli advanced down a depression 
in the preceding flows until it spread into the northern end of Butte 
Lake. This flow is quite reliably dated as having been erupted in 1851. 
On the surface of these last flows are several small cinder cones. 

Hat Creek Valley, which starts about 10 miles northeast of Lassen 
Peak, extends for about 25 miles to the northwest where it gradually 
merges into the Modoc Lava Plateau through which the Pit River has 
cut its canyon. The valley ranges in width from 1 mile to 4 miles. 
West of it are three prominent volcanic cones, Magee and Burney 
mountains and Stoney Peak, which rise above a complex of smaller 
volcanoes, all being part of the Cascade Range which ends south of 
Lassen Peak. 

The eastern margin of Hat Creek Valley is a prominent and only 
slightly eroded fault scarp, the displacement in part being mostly 
along a single fracture and in part being distributetl along a series 
of rougldy parallel and converging faults bordering step-blocks, each 
tilted eastward. At the south end of the valley the scarp is about 700 
feet high, while 9 miles north it increases to 1,.500 feet but this amount 
of dislocation is distributed along three fault blocks, each bounded 
by scarps. In contrast with this spectacular topography, tliere is no 
evidence that the west side of Hat Creek Valley was formed by fault- 
ing. It is true that two faults are present on this side, but the displace- 
ment is small and the blocks are downdropped to the west as on the 



[Bull. 158 

opposite side of the valley. Hat Creek Valley may be a large block 
tilted eastward at a gentle angle or a number of smaller blocks simi- 
larly tilted and covered by later lava. 

In the valley is a large How of basaltic lava, probably erupted 
within the last 2,000 years though exact dating is impossible. This 
flow was discharged from north-south fissures located near Old Sta- 
tion along the highway leading through La.ssen Volcanic National 
Park at the base of Sugarloaf Mountain. This peak is a lava cone 
capped by a cinder cone, both erupted after the dislocation along the 
faults above described had been largely completed. At the head of the 
flow is a series of spatter or drAlet cones ranging from 3 to 30 feet 
high and having depressions in the top which reach as much as 40 feet 
in depth. Evidently these cones represent accumulation of lava thrown 
from a series of lava fountains spaced along fi.ssures from which the 
magma was being erupted, a feature observed in some recent flows. 
Tongues of basalt lead from the spatter cones and merge with the 
main lava stream, showing that the principal source of the magma 
was that rising along the fractures. These tongues are describetl as 
having corrugated surfaces, the small ridges covering lava tubes 1 
foot to 2 feet high and 3 to 4 feet wide through which the molten rock 
moved after a crust had formed above. 

Some of the lava from the spatter cones flowed westward surround- 
ing several older basaltic cones, but most traveled northward .joining 
the main part of the How near Old Station. The flow near Old Station 
swept eastward from the source vents, then north down Ilat Creek 
Valley for a distance of about 16 mile. 

Lava tubes are common throughout the How but most are small. 
The best known and one to which travelers through the park often go, 

called Subway Cave, is about a mile northeast of Old Station. It has a 
height of 12 to 15 feet and can be followed for a distance of half a mile. 
Collapse of joint blocks from the rock has made possible entrance 
to the tube. 

The lava is much jointed and these fractures together with the 
numerous tubes make the flow highly pervious to water. Hat Creek 
is the only stream which flows continually over the flow. On the east 
side of the valley a stream coming from the plateau Hows northward 
for a distance of 5 miles before disappearing into the pervious lava. 
At the lower end of the flow, the water table is close to the surface of 
the lava so that pools of water fill depressions in its surface and these 
gradually merge into a stream. Rising River. 


Anderson, C. A., Volcanic history of Glass ^lountain, northern California ; Am. 
.tour. Sci., vol. 26, pp. 485-506. 1933. 

.Anderson. C. A., Volcanoes of the Medicine Lake Hichland, California : Univ. 
Ciilifornia Dept. Geol. Sci. Bull., vol. 25, pp. 347 422, 1!141. 

Williams, Howel, A Recent volcanic eruption near Lassen Park, California : 
fniv. California Dept. Geol. Sci. Bull., vol. 17, pp. 241-263, 1928. 

Williams, Howel, The history and character of volcanic domes: L"niv. California 
l>ept. Geol. Sci. Bull., vol. 21, pp. 51-146, 1932. 

Williams, Howel, Geology of the Lassen Volcanic National Park, California : 
fniv. California Dept. Geol. Sci. Bull., vol. 21, pp. 195-385, 1932. 

Williams. Howel, Mount Shasta, a Cascade volcano: Jour. Geol., vol. 40, 
pp. 417-429, 1932. 

Williams, Howel, GeoloRV of the Macdoel quadrangle, California : California 
Div. Mines Bull. 151, 1949. 

Flo. 98. 

^1..;;^. L.i.^sen V 
of the Chaos Ju 

Fig. 99. Raker Peak, Lassen ^'oU■anic Xntiona 
is plug dome ; right siile is a lava cone capped by a ci 
is part of the 1915 mud flow. After Iloirel Williani 

1 Park. Left s 
nder cone. In 

ide of the peak 
the foreground 



The Klamath Mountains include a rugged though not particularly 
high region lying west of the Cascade Mountains, south of the Oregon 
Coast Ranges, and north of the California Coast Ranges, being divided 
between the southwestern part of Oregon and the northwestern part 
of California. Many local names are applied to various ranges such as 
Siskiyou. Klamath, Marble, Scott Bar, Trinity Alps, and others, but 
in the ensuing description the term Klamath is applied to the entire 
area. Within the California section there are many magnificent scenic 
areas, both along the coast and within the mountains themselves. 
Much of the coast is boldly cliffed, the canyons are deep and narrow 
in most places, and the peaks and ridges rise boldly above. The higher 
mountains have been glaciated giving them particularly bold contours 
and in these areas are beautiful rock basin lakes. Fortunatelj- the 
Klamath country has not been so extensively penetrated by roads as 
have some other mountainous sections of the state so that the primitive 
character of the region is largely preserved. Some of the high points 
are Condrey Mountain (7,116 feet). Red Mountain (8,317 feet). China 
Mountain (8,551 feet) and Russian Peak (8,163 feet) in Siskiyou 
County ; Thompson Peak (8,936 feet), Caibour MounUin (8,563 feet) 
and Gibson Peak (8,378 feet) in Trinity County; and South YoUa 
BoUy (8,083 feet) in Tehama County. 

The principal drainage system is the Klamath River which starts 
east of the mountains in the Modoc Plateau and Cascade Range, even- 
tually flowing into the ocean about 15 miles south of Crescent City or 
30 miles south of the Oregon border. At the settlement of Weitchpec 
between 30 and 35 miles from its mouth, the Klamath is joined by its 
principal tributary the Trinity, the South Fork of which flows for a 
long distance through a great structural depression whose origin has 
not yet been worked out. Some other minor streams drain west into the 
Pacific and some eastward into the Sacramento River which has its 
source in a small lake on the eastern side of the Klamath region. The 
Sacramento River, together with the Pit and McCloud Rivers, which 
flo'v through the area, are the principal drainage lines in the eastern 
part of the Klamath Mountains. The picture has been altered some- 
what by the construction of Shasta Dam located on the Sacramento 
River a short distance below its junction with the Pit. This giant 
concrete barrier, principal element in the great Central Valley Project 
for flood control, irrigation, and other purposes, impounds a large 
reservoir extending up the canyons of the Sacramento, the Pit, and 
the McCloud. The last two rivers now enter this large artificial lake. 

Geologically tUf Klamath Mountains are sharply contrasted with 
the bordering ranges, for they are comprised largely of pre-Paleozoic 

and Paleozoic sedimentary rocks, volcanic rocks, and many intrusive 
bodies. Along the eastern side Tria.ssic and Jurassic strata are exposed 
and the intrusive masses may be partly or largely Mesozoic. The 
Klamath formations have been greatly deformed and many of them 
considerably metamorphosed. In contrast, the California section of 
the Cascade Range is comprised largely of Cenozoic volcanics while 
the California Coast Ranges consist almost entirely of Mesozoic and 

Fig. KM). Emerald and Sii|i|>liirc I,:ikes. Trinii.v Alps. Tin- 
two lakes occupy rock basins excavated by a glacier. Photo by 
Eattman Studio. 

( 139) 



[Bull. 158 

KiG. 101. Castlp ('ra;js, a stuck of Kninitnid rock intruded about I'M) million years iico and uncovered by erosion. Mt. Shasta is in 

the backsround. Photo courtesy ('. S. Army Air Corps. 




Cenozoic sediments and volcanics, with the oldest Mesozoic formations 
belonfrinpr to the late part of the Jurassic period. The ixreat bulk of 
Coast Ran-ie formations are Cretaueous and Cenozoic. On the south- 
west side of the Klamath Mountains, the natural boundary with the 
Coast Ranges would appear to be the South Fork of the Trinity River, 
but the South Fork Ranjre on its southwest side is comprised of 
Klamath formations and therefore must be included in that province. 

The Klamath Mountains are sharply distinguished also from the 
Coast Ranges in the character of their drainage systems. Fold-faulting 
of the Klamath area probably occurred in the late Jurassic when the 
Sierra Nevada and various other California ranges were created. The 
Coast Ranges are infant mountains now in process of development by 
fold-faulting which started in very late Pliocene and Pleistocene time. 
In the Klamath region, because of erosion which has gone on since 
Jurassic time, control of drainage by folded and faulted features 
evolved when the mountains first appeared has long since been wiped 
out. hence the streams do not follow structural trends. In the Coast 
Ranges, on the other hand, folded and faulted ridges, troughs, and 
basins are conspicuous, and the streams to a notable extent are directed 
by them. 

The Klamath Mountains lie in the path of the moisture laden winds 
which sweep eastward from the Pacific. Along the coast rather equable 
climate prevails, though the extremes are greater than in the Coast 
Range belt and farther south. 

Precipitation along the coast is moderately heavy, averaging 39 
inches annually at both Eureka and Crescent City, a few miles north. 
Within the mountains at Monumental (2.550 feet) there is an aston- 
ishing increase to 109.4 inches, but at other stations at the same or 
even higher elevations, the figures are much lower ranging between 
28 and 52 inches with the higher figures at higher elevations. Measure- 
ments are made at so few places that a very incomplete picture of 
precipitation over the Klamath area is -available. Undoubtedly over 
the higher ridges particularly in the western part precipitation ap- 
proaches or may exceed that at Monumental. Along the eastern base 
of the mountains there is sharp decrease, with annual averages of 
17 to 26 inches at three stations, Hornbrook, Treka, and Edgewood 
whose elevations range from 2.154 to 2,933 feet. At equivalent eleva- 
tions somewhat farther west, average annual precipitation ranges 
between 36 and 52 inches. Snowfall in the winter months in places is 
heaw reaching a measured maximum of 126 inches at Monumental 
and 108 inches at Gilta (3..300 feet). 60 miles to the southwest. At 
Yreka on the eastern border, the annual average decreases to 16 inches. 

The abundance of rain and snow gives many permanent streams 
through the region though there is material fluctuation in their volume 
because of the hea^•J' concentration of precipitation during the winter 

When viewed from higher peaks or ridges, the ruggedness of the 
region so impressive from canyon bottoms or in climbing the steep 
slopes in a measure departs, for most of the ridge tops have con- 
siderable similarity in elevation which from the coast inland 
and from south to north. By imagining the canyons to be filled in. one 
gains the impression of a former advanced landscape characterized 
by broad valleys separated by ridges of moderate height. Near the 
coast the elevation of the ridge tops ranges from 1.700 to 2.500 feet 
increasing to 4..500 feet 50 miles inland ; in places, as in the South Fork, 
Salmon, and Yolla Bolly Mountains, the elevation increases to 6.000 
or 7.000 feet. The ancient landscape evidently was warped and prob- 
ably faulted during elevation and has been very deeply dissected by 
the invigorated streams. 

Above the general level made by most of the ridges certain residual 
peaks rise for 1.000 to 5,000 feet and lower ones from 100 to 600 feet 
in height are common. Some of the higher areas undoubtedly represent 
erosion remnants but others may have reached their present position 
because of movements along faults. Among the highest sections in the 
California part of the Klamath Mountains are the Siskiyou Mountains 
between the Klamath and Rogue river basins, the Scott. Salmon, and 
Trinity Mountains which make the headward parts of divides between 
three large forks of the Klamath River flowing into it from the 

The Bullychoop Mountains in Shasta County marks the divide 
between the Trinit.v and the Sacramento rivers and the Yolla Bolly 
Mountains between the Sacramento and the streams of the California 
Coast Ranges. 

When the oldest and highest erosion surface was being developed 
at an elevation much lower than its remnants now possess, the streams 
ran transverse to the dominant structural trends of the region just as 
they do now. Apparently the Jurassic mountains had been sufficiently 
worn down so that the control of stream direction by folded and 
faulted ridges and depressions and other parallel structures had been 
largely wiped out. This surface must have been evolved by Miocene 
or early Pliocene time. Since then there have been various rejuvena- 
tions with streams returning to youth, later advancing to maturity 
and developing terraces below the level of the oldest landscape. 
Various terrace levels have been recognized, but they do not represent 
so continuous a landscape as that represented by the high level rem- 
nants. In late Pliocene and Pleistocene time, the principal uplift of 
the Klamath region occurred and with it the great amount of erosion 
which has evolved the rugged landscape of today. 

In the higher mountains moderate ice attack occurred during the 
glacial stages, both from permanent ice fields and from true glaciers. 
The usual cirques, U-shaped valleys, hanging valleys, rocks basins, 
and moraines are present, though on a relatively limited scale. The 



[Hull. 158 


^:,^> _ 




^^>. -^ ' 

'. ->-^*.> 


Flu. lie Klaiuutli .MouutuiiKs near \\'fa\ cr\ iUe. I'liuto by J. 11, Eastman. 

history and extent of the ■rlaciatioii has not been worked out, but it 
definitely was no match for that in the Sierra Nevada. 

One of the best known sections of the Klamath Mountains is the 
Castle Cra?s west of Duiismuir. The rafrtred spires and pinnacles have 
been eroded into a much jointed stock of };ray firanitoid rock which 
was probably intruded at the time of the Jurassic foldinpr which built 
the first mountains in this region. The stock has been exposed by the 
deep erosion which has followed the fold-faultinp; of this distant time. 
Another much more scenic area is the Trinity Alps, one of the highest 
and most rugped parts of this province, located about 15 miles north 
of Weaverville. The peaks and valleys in part have been moderately 
glaciated and conseipiently their contours are bolder than the average 
for the region. A number of beautiful little lakes lie high up in the 
deep, narrow canyons. 

In a number of places in the Klamath Mountains such as near 
Weaverville and Hyampom there are basins containing moderate 
thicknesses of sediments and some volcanic rocks principally of 
Eocene age. These deposits are notable, as Tertiary sediments are 
rare in the entire province. Probably the basins have been evolved by 
faulting which very likely occurred after the deposits were laid do^vn, 
protecting them from extensive erosion. 

At various places along the coast there are elevated shore features — 
battered wave-cut cliffs, erosion and deposition terraces and eminences 

that once were islands. One terrace has been reported at an elevation 
of 1,5(10 feet, another prominent one at least a mile wide in jilaccs 
at 1,000 feet, and a third at 500 feet. There are others less sharply 
defined. Unfortunately studies of the coast line in this part of <'ali- 
fornia go back many years and future investigations undoiditcdly 
will alter the picture we now have of the uplift and erosion that 
produced these features. Whether the highest staiuling surfaces 
mentioned above actually are marine terraces remains to be con- 
firmed; that there are some at lower elevations is certain. Prominent 
clitfs with the usual attendant features are now being eroded along 
most of the coast in the Klamath region giving a bold shore landscape 
which in places is magnificent. 

A notable man-made feature is the huge, three-pronged artificial 
lake impounded behind the huge Shasta dam which has been con- 
structed on the upper Sacramento River near the site of the former 
copper smelting and mining town of Kennet some 16 miles north of 
the city of Redding. This immense concrete barrier is 5G0 feet high 
and .3,500 feet long across the crest. When the water is in the reservoir 
the vast lake is a beautiful sight, but when it falls there is an ugl.v 
strip along the shore littered with sediment and dead vegetation. The 
reservoir is part of the giant Central Valley Project, a combined flood 
control, water supply, and power generating system which will be of 
growing importance to the Great Valley as agriculture and industry 
of that region develop. 

Oiled road access to the Klamath Mountains is limited and even 
dirt roads are none too numerous. Highway 101 runs along the 
and 299 leads from Eureka, principal city of the northern California 
coast, to Ivedding at the north end of the Sacramento Valley. A branch 
taking off at Willow Creek goes into Iloopa Valley. Highway 199 
leaves 101 at Crescent City and crosses the northwest part of Cali- 
fornia's Klamath Jlountains on its way to Grants Pass in Oregon. 
An oiled road follows the Klamath River for many miles, and another 
also branching from Highway 99 goes to Etna. On the eastern side 
Highway 99 traverses the Klamath Mountains from the Oregon border 
to their junction with the Sacramento Valley. By bridge this highway 
twice crosses the immense reservoir behind Shasta Dam. 


Diller, J. S., Tfrtiar.v revolution in the topogruphy of the Pacific Coast: U. S. 
Geol. Surve.v Fourteenth Annual Report, 1802. 

Diller, J. S., TopoKraphic development of the Klamath Mountains: U. S. Geo]. 
Survey Bull. 196, 1902. 




Almost completely enclosed by mountains is one of the most notable 
structural depressions in the world, the Great Valley of California 
more than 400 miles long and avera-jin*; 50 miles in width. Most of the 
valley lies close to sea level in elevation, but along the margins in 
places it rises somewhat higher, the maximum being about 1,700 feet 
at the tops of steep alluvial fan slopes which rest against the mountains 
at the southern end. Most of the eastern boundary is not much more 
than 500 feet high but the western is lower, ranging from 50 to 350 
feet along the greater part. The basin has a single outlet, Carquinez 
Strait, crossing a section of the Coast Ranges through which the 
Sacramento River flows into San Francisco Bay. In the part of the 
Sacramento Valley near Carquinez Strait there is considerable land 
standing below sea level now protected from flooding by natural levees 
and artificial dikes. 

Bordering the Great Valley are the Tehachapi, Sierra Nevada, 
Cascade, Coast and Klamath Mountain Ranges. The basin has existed 
for a long time; record of it is found from the folding which elevated 
the Sierra Nevada, the Klamath, and other California mountains in 
the late part of Jurassic time. During the Cretaceous period and much 
of the Cenozoic era, the basin extended over most of the area now 
occupied by the Coast Ranges and had its western margin along the 
base of the old land, Cascadia, which has since disappeared. At times, 
such as in the late Jurassic and Cretaceous periods, the lowland was 
under water. In the land now occupied by the Coast Ranges local 
deformations and volcanic activity altered the topography of different 
sections, particularly during the Cenozoic era, and in the present 
valley area there were oscillations above and below sea level. Late in 
the Pliocene epoch the compression forming the Ranges started 
and continued throughout the Pleistocene generating a fold-fault 
mountain system of moderate height. The elevation of this moun- 
tainous belt materially narrowed the width of the basin, developing 
the present outline of the western margin late in geological time. 
Into the Great Valley flowed the drainage from the surrounding 
mountains, most of the water coming from the Sierra Nevada, the 
Cascade and Klamath Mountains. These streams have deposited im- 
mense quantities of sediment forming a great flood plain with alluvial 
fans around the mountain base. Most of the streams joined two trunk 
rivers, the Sacramento in the north and the San Joaquin to the south. 
The Kings River which enters the Great Valley from the Sierra 
Nevada south of the San Joaquin has formed a huge alluvial fan that 
projects across the valley, joining one formed by a Coast Range stream, 
Los Gatos Creek, shutting off the part of the valley to the south as an 
interior basin. Formerly this section was occupied by shallow lakes, 

10— 6045S ( 

but most of the water has been drained to increase agricultural area. 
The largest of the lakes was called Tulare which gave its name to the 
basin, though actually the area contained others as well. 

Sacramento Valley 

The term Sacramento Valley commonly is used for most of the low 
countrj- through which the Sacramento River flows. However, there 
is a considerable range of low hills north of Red Bluff developed in a 
broad anticline that separates the section still farther north from the 
much larger stretch to the south. This northern division includes a 
number of minor valleys which deserve separate names. 

The Sacramento River has its source in a small lake on Mount Eddy, 
one of the peaks of the Klamath Mountains, about 50 miles south of the 
northern boundary of California. After flowing eastward for about 
12 miles, it turns to the south for 370 miles to the head of Suisun Bay, 
50 miles northeast of San Francisco, where it unites with the San 
Joaquin River. North of Redding the Sacramento was joined by the Pit 
River which flows from Goose Lake on the east side of the Warner 
ilountains in Modoc County across the great stretch of lava beds into 
which it has cut a deep, narrow gorge. A few miles east of its junction 
with the Sacramento, the Pit received the waters of the McCloud River 
whieli comes from the Jlount Shasta section of the Cascade Mountains. 
Many other tributaries are added farther south, mostly coming from 
the Sierra Nevada. 

The main part of the Sacramento Valley is about 150 miles long. 
Its greatest width is about 40 miles and its elevations range from 
slightly below sea level to about 300 feet above in the main section. 

Most of the surface is quite flat and monotonous, a product of the 
long time during which sediment has been deposited in this great 
trough. In places, some folding and faulting have occurred, raising 
these sections above the general level and making it possible for 
streams to develop hilly or gently rolling topography quite sharply 
contrasted with the normal landscape. In the middle of the valley, 
quite discordant with its even contour, are the prominent Marysville 
or Sutter Buttes. The two principal eminences. North Butte and South 
Butte, are 1.863 and 2,132 feet respectively above sea level, the highest 
points in the entire basin. 

Five natural divisions are recognized in the Sacramento Valley — 
the red lands standing more or less conspicuously above the present 
flood plain which is comprised of low plains, river lands, flood basins, 
and islands. 

Red Lands. The red lands are belts of hilly or gently undulating 
country found in places along both sides of the Sacramento River, and 
generally sloping toward the axis of the valley. These areas once were 
almost as even surfaced as the lower parts of the valley today, having 




[Bull. 15S 

been constructed by the various streams coming from adjacent moun- 
tains and representing a flood plain and alluvial fan level higher than 
the present one. Later this plain was deformed by gentle folding or 
faulting which made it possible for the streams that built them to 
erode instead of deposit. 

In the northern part of the Sacramento Valley, the red lands extend 
almost to the middle of the valley and the Sacramento River flows 
through a wide, shallow trench bordered by discontinuous bluffs which 
it has eroded through them. On the east side of the river, the red lands 
are narrow and not sharply separated from the low plains in the 
vicinity of Red Bluff, but farther south their width and definiteness 
increase until at Vina thej' are about 4 miles wide and are separated 
from the low plains by bluffs about 50 feet high. In this section they 
are cut by streams coming from the Cascade Mountains which have 
eroded narrow, terraced valleys. South of Vina, the red lands are 
lower and disappear before reaching Chico. 

West of the Sacramento River, the border of the red lands is a con- 
spicuous bluff which extends from Red Bluff southward to Tehama, 
while south of that city to the Glenn County line, the boundary is 
poorly defined with more or less detached hills and knobs extending 
down to the river. 

Prom Chico southward to the Yuba River, the red lands occupy a 
considerable area on each side of the deep, terraced gorge of the 
Peather River. From Chico southward and from the Yuba River 
northward, the red lands increase from scattered higher patches sur- 
rounded by the low plains to wider and wider tracts of highland, until 
on each side of the Peather River they form broad bench lands stand- 
ing from 325 to 425 feet above sea level. In the region south of the 
Yuba River, east of the Peather River and the American basin, the 
red lands are only slightly elevated above the present level of the 
streams. They rise gradually to an elevation of 100 to 300 feet but 
merge into the low plains so that a definite boundary cannot be drawn 
between the two. 

On the west side of the Sacramento River, the red lands are less 
extensive than on the east, but are much more sharply defined, because 
uplift has made a sharper break between them and the low plains and 
because the soil in the low plain is yellowish. This color difference is 
not so conspicuous on the east side of the Sacramento River, as the 
reddisli color of the upland areas is not strongly developed. The red- 
dish color has been produced by oxidation of iron molecules contained 
in the sediment. Prom Stony Creek south to Williams, the red lands 
occupy small areas flanking the foothills of the Coast Ranges and rise 
about 100 to 200 feet above the streams flowing through them. Their 
much dissected surface slopes abruptly from the foothills to the low 
plains. Between Willows and Williams the red lands increase in width 
and ruggedness. 

The most extensive area on the west side of the Sacramento River 
runs from Williams southeastward to Cache Creek. The southern part 
is called the Hungry Hollow Hills but this terra is applied by some 
to the wliole area. This section is a plateau 100 to 450 feet above sea 
level, bounded on the northeast by a remarkably straight and uniform 
though somewliat eroded fault scarp. The southern part has been 
greatly dissected into hill-valley landscape, but farther north there 
are remnants of the flat-topped plateau. 

South of Cache Creek, but offset to the west, is another tract of red 
lands also apparently bounded by a fault scarp, which fringes the 
foothills increasing in width until near Winters it is a half mile to 
2 miles across. 

On the north end of the narrow throat through which the San 
Joaquin and Sacramento Rivers find their way to Suisun Bay arc 
the Montezuma Hills, circular in groundplan and about 12 miles in 
diameter with their west side joining somewhat detached foothills of 
the Coast Ranges. This is a much eroded remnant of red lands sloping 
from elevations of 250 to 300 feet above sea level on the southwest to 
only 25 feet on the northeast where it merges with the surface of the 
low plains and of the Yolo Basin. On the south and southwest, the 
Montezuma Hills are bounded by sharp bluffs rising above the Sacra- 
mento River or above narrow plains bordering the salt marshes of 
Suisun Bay. 

River Terraces. Streams tributary to the Sacramento River have 
terraced valleys in the edges of the foothills and in the red lands. The 
terraces vary in width and height in different valleys, but in a given 
valley, they are constant in their relative position above the stream ; 
they generally are detached remnants along the valley sides. There are 
two principal terrace levels, the upper level being 20 to .50 feet below 
the general surface of the red lands, the lower 10 to 20 feet below 
that and 5 to 20 feet above the flood plains now in process of 

Only streams rising in the mountains and crossing the valley border 
have terraces. Their history indicates three stages of valley cutting, 
widening, and filling with sediment, the last being now in process. 
Causes of the evolution of the terraces include intermittent uplift 
with consequent limited downeutting by the streams until their down- 
cutting power became so small that they began to widen the valleys 
producing erosion terraces later covered with flood sediment. The 
known climatic changes of the Pleistocene also may have played a 
part. The history of the region is not sufl3ciently well known to 
determine the factors involved. 

Loiv Plains. The low plains lie between the red lands and the river 
lands, but where the red lands are absent they stretch to the of 
the mountains. They stand somewhat lower than the red lands and 
their surface is almost level. The plains have been built by the streams 




coming from the mountains wliich have eroded the red lands and the 
evenness of their surface results from sedimentation which is still 
goinpr on. They are the highest portion of the flood deposits being 
formed by the streams. 

The low plains are comprised partly of alluvial fan and partlj' of 
ordinary flood plain deposits. The fans are characteristic of the 
mouths of intermittent streams which have carried large quantities 
of debris from the mountains, depositing very rapidly as they emerge 
from canyon mouths. The two most notable examples are the fans of 
Stony and Chico Creeks, both broad and rather gently sloping. In 
some places closely spaced fans have coalesced into alluvial aprons as 
at the foot of Hungry Hollow Hills in the vicinity of Arbuckle. 

On the west side of the Sacramento Valley from Williams south to 
the Montezuma Hills, intermittent streams issuing from the hills 
carrying fine setliment have developed raised banks on either side 
which are natural levees rather than fans; they stand from 3 to 20 
feet above the bottoms of the channels and range in width on each 
side of the channel from 500 yards to 3 miles depending on the size 
of the stream which has produced them. 

The streams forming these levees not only build up their banks 
but also deposit silt in their channels, thus raising their level and 
lowering the slope over which they flow. Bed and banks together 
slowly gain in elevation forming inconspicuous double crested ridges 
standing 10 to 25 feet above the lowland on either side. They show prin- 
cipally at time of flood since the lower adjacent areas are under water 
while the long sinuous ridges stand above. \ot infrequently flood 
waters burst through a levee starting a new channel with banks built 
up along it similar to the old, leaving abandoned channels below the 
point of diversion and giving a series of forking ridges. The levees 
along these intermittent streams are similar in character to those 
along the permanent rivers like the Sacramento, but are much smaller. 

Toward the sides of the Sacramento Valley the low plains merge 
into and are represented by the more actively forming flood plains 
of tributary rivers, which are of two types — those of permanent and 
those of intermittent streams. 

In the first group are the flood plains of the Mokelumne, the 
Cosumnes. and the American Rivers, which are a half mile to 2 miles 
wide and rise from a few feet to 20 feet above the rivers. Through the 
plains the rivers run with sinuous but not strongly meandering 
courses. Human activities have so changed conditions along the Bear 
and Yuba Rivers that they no longer have their original appearance. 

River Lands. The river lands are quite narrow belts rising 5 to 20 
feet above adjacent land and extending along both sides of the two 
principal streams in this portion of the valley, the Sacramento and the 
Feather. They are natural levees which have very gentle slopes toward 

the flood basins or adjacent low plains, and have been built in recent 
time by overflow from the rivers. The levees do not stand very high 
above their surroundings, but their elevation is enough to make them 
habitable, their soil arable, and thus to separate them from the 
swampy and frequently submerged lands through which they run 
for many miles. 

Flood Basins. On both sides of the Sacramento River between the 
natural levees or river lands and the low plains are broad, shallow 
basins locally known as tides because of the hea^y growth of tules or 
rushes which they formerly supported. There are five principal 
basins — Butte, Colusa, Sutter, American, Yolo, and two smaller 
ones — Marysville and Sacramento. 

These areas are dry most of the year or sometimes for whole sea.sons, 
but, during major floods, they are inundated forming shallow lakes. 
Before reclamation had been undertaken along the river, about 60 
percent of the valley was subject to overflow, including the basins, 
the river lands, and a considerable portion of the low plains. 

The flood basins are broad, shallow troughs filled during floods by 
the side streams which sweep across the low plains in broad sheets 
and by rivers discharging into them through definite channels, or 
overtopping the natural levees and the river lands. Deposition in the 
basins comes primarily from standing rather than from running 
water, hence their surfaces are almost ideally even, though there is a 
gentle slope toward the center and the downstream end of the basin. 
The soils are hea\y, less satisfactory for ordinary agriculture, but 
successfully used for growing of rice. 

Islands. At Clarksburg, minor channels break away from the Sac- 
ramento River, flowing for a distance, then joining other channels 
or the main river. These many channels therefore are interconnected 
and also are connected with similar channels of the San Joaquin 
River. Both the Sacramento and the San Joaquin enter Suisun Bay 
by separate courses in a gap about 4 miles wide between the Monte- 
zuma Hills and the Diablo section of the Coast Ranges. On account 
of the various channels above the river mouths part of the discharge 
of the Sacramento may enter Suisun Bay through the San Joaquin 
River and vice versa. 

Between the channels are islands bounded by natural levees formed 
by these minor branches of the Sacramento and therefore basin shaped. 
Tiuler natural conditions the islands were partly covered with water 
during much of the year and were almost completely overwhelmed dur- 
ing high floods. The tide raised and lowered the level of water over large 
areas, thus helping to scour out and keep open the minor channels. 
The natural levees therefore are composed of silt and loam deposited 
during the overflow while the central part of the islands contain 
peaty material formed from decaying vegetation which grew in them 
when covered by water. Artificial levees have been built on top of the 



I Bull. i:. 

Flo. lO.'i. liike alniip SiicrannMitn KiviT. WondliiiKl Ishinil in foreKroiind. Material 
usetl to build dike was obtained by dredging the river. Photo hy Mary Rae llill. 

Fig. 104. 

^ '*■*', 

Victoria Island in Sarranionto Uiver. Asparagus fields in background. 
Photo by Mary lioi Ilili. 

natural prcventiufj tlie floodiiiji of former years. Rainwater aud 
spcpase from the river are drained by a oanal cut tliroufih the central 
flat of oaeh island leading to its lower part, and pumping stations 
are maintained to lift the water over the river banks. During the dry- 
season, water is pumped from the river for irrigation and the surplus 
runs to the lowest end of the island where it is pumped back into the 

Marysville or Sutter Buttes 

Kising Conspicuously above the almost level floor of the Sacramento 
Valley about ay.'miles northwest of the city of Marysville are the 
Marysville Buttes or as they are locally known the Sutter Buttes. 
Occupying an almost circular area about 10 miles in diameter, their 
liighest point stands 2,132 feet above sea level and almost that amount 
above the surrounding lowland. In any view from a distance two 
distinct features stand out — peripheral slopes extending in a long, 
gentle curve to a height of 600 or 700 feet and tlie abrupt and ragged 
peaks and domes making the central part of the With almost 
featureless plains extending for miles round about, the buttes make 
a startling landmark visible for long distances. 

The Marysville Buttes are a volcanic mass, principally a laccolithic 
intrusion which is a roughly mushroom-sbaped body of small size 
that deformed the covering strata into an anticlinal dome as it wits 
being emplaced bi>low the surface. Dtiring and after the intrtision of 
the igneous mass, the overlying layers were largely stripped away. 
Then steam explosions develoiied a central crater by blasting through 
the core of the laccolith and constructed a volcanic cone. Other minor 
volcanic eruptions also occurred. 

Prior to the intrusion of the laccolith, the present site of the buttes 
seems to have been a plain like the rest of the Sacramento Valley and 

I-'ic. 10.1. View of Mar.vsvillc (Sutter) Buttes from near Williams, 20 mile."* 
St. South Butte is high i>eak on right ; West Butte is central peak. ,l//cr llotrcl 






was underlain by nearly flat-lying sediments such as are being laid 
down in many places today by the streams which flow through the 
valley. The rise of the magma was forceful enough to arch the strata 
above it until the cover could yield no further to this type of defor- 
mation ; it then was broken apart by a series of faults part of which 
are radial to and part concentric with the margin of the laccolith. 
The blocks thus produced were tilted outward at various angles. 

The intrusive body apparently has steep sides toward the top and 
flattens out irregularly near the margins. The top of the body was 
covered by an uneven blanket of sediments; how much rock has been 
eroded from the blanket and intrusion is uncertain but evidence 
rather strongly indicates that the tops of the buttes are not far below 
the original surface of the body. Also how high a dome was originally 
produced cannot be determined because the roof was being eroded 
while deformation was proceeding under the impetus of the rising 
magma. Field evidence indicates that when the later volcanic explo- 
sions occurred, the sedimentary cover had been stripped off about as 
it is today, showing that it has only recently been denuded of the cover 
of volcanic debris imposed upon it. 

Following emplacement of the laccolith but before most of the 
explosive eruptions occurred, necks or stocks of rhyolitic composition 
were intruded both into the margin laccolith and the surrounding 

TVhen the sedimentary cover had been largely removed from the 
laccolith, violent steam explosions evolved a central crater and minor 
craters near the margins. \o fresh magma was erupted, the products 
being fragments of previously consolidated rocks erupted at relatively 
low temperatures. The first outbursts were vigorous, indicating long 
accumulation of gas pressure under the mountain, but the intensity 
decreased and intervals between the various explosive cycles were 
long enough to permit deep erosion of debris which had been pre- 
viously blasted out. This would indicate that magma, still being 
intruded at depth, was crystallizing and expelling gas which accumu- 
lated until the explosions began. 

Fio. 106. Stages in the development of Marysville (Sutter) Buttes. /, Original 
structure of sediments under Saeraroento Valley. 2. Intrusion of laccolith and dom- 
ing of sediments. 3, Erosion of the sedimentary cover and laccolith. ^, Intrusion of 
rbyolite domes. 5. Further intrusion of rhyolite and explosions forming volcanic 
cone over eroded surface of laccolith, domes, and sedimentary ring left from erosion 
of original cover of laccolith. 6, Production of existing topography by erosion. After 
Hoteel Wiiliami. 

Fio. 107. Generalized section across the Marysvillc (Sutter) Buttes showing 
by solid line the present topography, by the lower dashed line the surface of the 
laccolith believed to have been stripped of its sedimentary cover before the explosive 
cycle started, and by the upper dashed line the ijossible form of the principal cooe 
built by explosions. .4/(er Iloirel WilliamM. 



I Bull. 158 

Before the explosive phase commenced, tlie mountain was a more 
or less cone-shaped eminence with high points standing about 3,000 
feet above sea level. The explosions opened a roughly cylindrical vent 
in the central part of the laccolith which is now filled with the products 
of the last eruptions. The violence of the eruptions varied, for some 
threw out angular boulders up to 15 feet long while others emitted 
only fine-textured debris. 

The more forceful outbursts erupted great masses of coarse as well 
as fine fragments which apparently swept down the sides of the cones 
in avalanche fashion. When the eruptions were less intense, the prod- 
ucts were finer and formed well-bedded deposits which contrast with 
the chaotic nature of the avalanche debris. Also there are other 
deposits formed by streams which flowed down the slopes of the 
volcano both during the explosive phases and episodes of quiescence. 
The cone which was formed above the laccolith probably had an ele- 
vation of about 5,000 feet. 

Besides the major eruptions, there were many minor ones from the 
principal crater and from smaller openings along and near the 
margins of the laccolith. The explosions of the subsidiary vents 
doubtless built small cones. 

The final explosive products are fine tuffs which seem to have filled 
the crater of the volcano ; in some exposures they are more than 1 ,000 
feet thick. From their field relations it appears that they were erupted 
from a long, narrow fissure located near a crescentic valley in the 
southwestern crater wall. 

For a time, the volcanic cone must have been an imposing edifice 
in this very flat region, but now most of it has been removed so that 
the resistant rock of the laccolith now makes up the principal mass 
of the buttes. 

San Joaquin Valley 

The larger part of the Great Valley, extending southward from the 
Cosumnes River and Suisun Bay is called the San Joaquin Valley, 
although its entire area is not drained by the San Joaquin River and 
its tributaries. The southern, more arid third, extending from the 
Kings River to the base of the Tehaehapi Mountains, has no surface 
outlet under normal conditions, and the surface waters accumulate 
in Tulare Lake and Buena Vista Reservoir. Tulare Lake formerly 
received a portion of the excess flow of the Kern River, but by means 
of a restraining dike, water is kept out except when floods break 
through. The original lake bottom has been converted principally 
to wheat-growing land. 

The streams draining from the Sierra Nevada bring practically all 
of the water reaching the San Joaquin Valley, hence their volume is 
many times greater than that of streams coming from the other 
bordering highlands and their flow is much less erratic. 

This strong dominance of drainage from the eastern side has given 
the valley an unsymmetrical form, for the axis or line of lowest 
elevation is much closer to the Coast Ranges than to the Sierra Nevada. 
In places the axis even lies along the base of the western ranges, but 
in other localities the western slopes may reach half the width of the 
eastern as between Los Gatos and Cantua creeks. The slopes of the 
western side are somewhat steeper than those of the eastern. 

This unsj-mmetrical cross section, which in most places is not char- 
acteristic of the Sacramento section, results from the greater aridity 
of climate. The streams, overloaded with sediment because of decreas- 
ing volume as they reach the lower, drier mountain slopes have formed 
conspicuous alluvial fans, the larger, of course, growing at the mouths 
of the eastern streams. 

Over the fans the streams discharge in numerous channels flowing 
from the apes at the mouth of the canyon in different directions down 
the slope. Most of these distributaries as they are called travel out- 
ward on the sediment of the fan into which they have cut fairly deep 
trenches, but some from the San Joaquin River northward have eroded 
into the bed rock below the fan to a depth not exceeding 100 feet, the 
result either of recent elevation of the Sierra block or change in stream 
volume, the actual cause not yet being known. 

Tlie west side fans, particularly near the middle and southern parts, 
are steep and symmetrical, features characteristic of areas of slight 
rainfall quite unevenly distributed where the streams are smaller and 
have greater fluctuations in volume. The eastern fans, on the other 
hand, are much larger, more gently sloping, and less clearly defined. 

On the eastern side the Kern River fan has gro^\Ti westward against 
the McKittrick Hills isolating the Buena Vista basin south of it. 
Originally shallow Buena Vista Lake occupied part of the basin and 
during unusually rainy seasons there was overflow northward into 
Tulare Lake. Later on dams were built changing the natural condi- 
tions, impounding the waters of Buena Vista reservoir. Northward, 
the effect of aridity has been expressed by the building of the great 
Kings River fan which has joined one from Los Gatos Creek flowing 
from the Coast Ranges forming a low ridge behind which is the Tulare 
basin. Part of the water from the streams south of the barrier was 
impounded to form Tulare Lake which, when present, was very shal- 
low. Because of this and the fluctuating water supply, the lake varied 
notably in extent from year to year. There is no evidence that overflow 
from Tulare Lake ever went northward into the San Joaquin drainage. 

North of Tulare basin, discharge from the streams is great and con- 
stant enough to prevent formation of .such dams and an open channel 
is maintained by the San Joaquin River to Suisun Bay. The trunk 
river meanders sluggishly through its flood plain. 

Along the lower course of the San Joaquin, the topographic picture 
in general is similar to that along the Sacramento as it is developed 




Fig. lOS. Meanders of the San Joaquin alone its floo<l plain. Photo courtesy Fairchild Aeriat Surveys. 



[Bull. 158 

under somewhat more humid conditions. Large areas along the river 
are annually inundated by flood waters except where protected by 
artificial additions to the natural levees. The major floods occur when 
both the San Joaquin and the Sacramento are in flood at the same time. 
North of the mouth of the Stanislaus River, 20 miles south of Stockton, 
numerous channels diverge from the San Joaquin as from the Sac- 
ramento, isolatin<r islands similar in topography to those already 

The great contrast between the two major sections of the Great 
Valley is found in the southern, arid San Joaquin portion where the 
surface is a combination of alluvial fan surfaces with intervening 
shallow basins of the playa type, the Tulare and the Buena Vista. 
Farther north and throughout the Sacramento section, fans are less 
.striking because of the greater amount of rainfall, and although they 
are present along the valley margins, the main feature of the valley 
is the flood plain. 

The Kettlenian Hills lie close to the eastern base of the California 
Coast Ranges about 10 miles .southeast of Coalinga in the San Joaquin 
Valley. They form a slightly arcuate low range having a northwesterly 
trend, a length of about 30 miles, and an average width of 4 to 5 miles. 
The hills rise rather abruptly several hundred feet above the San 
Joaquin Valley to the east and are separated from the Coast Ranges 
by the almost flat Kettleman Plain which is 3 to 5 miles wide. The 
greatest elevation of 1,366 feet above sea level is at the northern end, 
from which there is a decrease southward until the hills merge almost 
imperceptibly with the even surface of the San Joaquin Valley. The 
Kettleman Hills are the main part of the isolated outermost foothills 
of the Coast Ranges which extend southeastward from the mountain 
front along the axis of the large Coalinga anticline. Three major anti- 
clines comprise the Kettleman Hills, named respectively North, Middle, 
and So\ith domes; they have echelon alignment and are offset. North 
and Middle domes are doubly plunging anticlines, that is their axes 
are inclined in two directions whereas South Dome plunges north- 
westward and is overlapped on the south by the alluvium of the San 
Joaquin Valley. The whole line of folds of which the Kettleman Hills 
are a part extends from Anticline Ridge to Lost Hills, a distance of 
about 70 miles. 

South and Middle domes are separated by Avenal Gap, an alluvium- 
floored depression extending from the Kettleman Plain to the San 
Joaquin Valley. No similar feature lies between North and Middle 
domes, the boundary between them being marked by decrease in 
ruggedness and change in trend. North Dome is the highest of the 
three and is most deeply eroded. Its culminating point. La Cima, 
stands about 600 feet above the Kettleman Plain and 900 feet above 
the San Joaquin Valley. 

The Kettleman Hills have been developed by deformation of a sur- 
face of very low relief which had been etched into sedimentary beds 
of Cenozoic age and apparently extended far beyond the limits of the 
area. The deformation is believed to have resulted from renewed fold- 
ing along the already existing Coalinga anticlinal belt. The erosion 
surface elevated by the deformation has been largely destroyed within 
the area of the hills. The domes contain two concentric rows of hills 
separated by shallow valleys excavated in weaker strata, an cscarp- 
ment-cucsta topography common in such structural settings. The 
crests of the hills in some places may represent parts of the old sur- 
face somewhat modified by erosion. One nearly flat remnant of the 
surface about a mile long and a quarter of a mile wide shows near 
El Prado at the north end of the Kettleman Hills, and other smaller 
remnants are present elsewhere. A lower erosion surface evidently 
formed by trenching of the older surface and broadening of the new 
valleys shows in some places. The deformation which gently folded 
and elevated this erosion landscape certainly occurred during Pleis- 
tocene time and probably rather late in the epoch. 

The entire Kettleman Hills area is characterized by rounded hills, 
but, in most of North Dome and on the west side of Middle Dome, the 
lower parts of the stream valleys are relatively narrow and steep sided. 
Locally the hill slopes are gullied into badlands, since the weak rocks 
are insufficiently protected by vegetation from the attack of torrential 
rains. The drainage is all intermittent, but, when it flows, transports 
enough sediment to add to alluvial fans which have formed at the 
mouths of the gorges where they open onto the adjacent plains. The 
headwater streams of North Dome have relatively deep, narrow val- 
leys, but the lower parts of some of them have reached maturity, are 
widening their valleys, and are depositing sediment over the terraces 
they have cut. 

Small patches of sand dunes are found here and there. In the San 
Joaquin Valley immediately adjacent to the Kettleman Hills, there 
are long northwestward-trending ridges of sandy material which some 
have suggested as eminences resulting from recent faulting but which 
actually may be old sand dunes of considerable size modified by 
later erosion. 


Bryan, Kirk, Geolopy and water resources of the Sacramento Valley. California : 
U. S. Geol. Survey Water-Supply Paper 495, 1023. 

Mendenhall. W. C, and others. Ground water in Snn Joaquin Valley, California : 
U. S. Geol. Survey Water-Supply Paper 308, 1916. 

Woodring, W. P., and others. Geology of the Kettleman Hills oil Held, California : 
U. S. Geol. Survey Prof. Paper 195, 1940. 






I Hull. 158 


Ku;. Uo. KettieiiKiii Hills, arilKlinal iloiiies in the southwestern part (if the San .I.iaiiuin Valley. I'holo :iiiiih\^y FnirrhUd Aerial Nuini/». 




Tlie California Coast Ranges form a physical province about 400 
miles lonji and 50 miles wide between the Pacific Ocean and Great 
Valley. They are composed chiefly of late Jurassic and youii^'er for- 
mations, and their topo^rraphy is controlled by folds and faults. The 
province contrasts sharply with the older Klamath Mountains to the 
north. The Coast Ran<res adjoin the Transverse Ranges to the south, 
the San Rafael Mountains being the southernmost coast ran-ie. The 
Coast Ranfres in most places rise abruptly from the shore line, their 
western marj.'in being marked by prominent sea cliffs. On the eastern 
side, the break between the mountains and the Great Valley is generally 
rather abrupt. 

Along the coast the climate of the Coast Ranges is controlled by the 
the moisture laden winds sweeping on shore from the Pacific Ocean. 
The temperature variations between day and lyght are normally small, 
summers are cool, winters moderately warm, and there is considerable 
fog. Prom south to north in the province, temperature variations in- 
crease, there is greater contrast between summer and winter, fog is 
more frequent and lasts longer, and rainfall increases. Snowfall is 
uncommon at low elevations except in the far northern part but the 
mountains, especially from San Francisco north, receive not infrequent 

The part of the Coast Ranges that is best knowai extends from the 
San Francisco Bay region to Santa Barbara County. The first deci- 
phered chapter of the history begins with the formation of a com- 
paratively small geosyncline lying between the ancestral Jurassic 
Mountains, particularly the Klamath, Sierra Navada, and Transverse 
Range sections, and a land mass called Cascadia, which lay west of 
the present shore line. During the latest part of the Jurassic and most 
of the Cretaceous periods, dominantly clastic sediment was deposited 
in the basin, the debris being derived principally from the western 
land. There were interruptions when the land rose above sea level, 
especially at the end of Cretaceous time when there was some folding 
and faulting. Throughout the Cenozoic down to the last epoch the 
basin oscillated above and below sea level, though the influxes of the 
ocean were not so extensive as in the two preceding periods; in addi- 
tion the land was less stable as shown by folding and faulting and by 
the products of volcanic activity. When above the ocean the relief of 
much of the Coast Range belt was similar to that of the Great Valley 
today, with which it was then coextensive. 

In the middle part of the Miocene epoch, compressive deformation 
began and gradually became stronger causing part of the Coast Range 
region to rise as ridges above sea level while other parts remained 
below and received sedimentary deposits. IIow much of the belt became 
land to be eroded we do not yet know. The rather weak compressive 

movements continued at intervals through the earlier part of the 
Pliocene epoch and became verj' much intensified in the later part 
of that time when the entire Coast Range belt seems to have been 
strongly folded and faulted, with the deformation being strongest 
near the coast and less pronounced eastward. A still more important 
deformation of similar type started in the middle Pleistocene, stamp- 
ing the general features of the present landscape on the Ranges 
and establishing the main features of the drainage. Subsequent 
changes along the coast and inland seem to have been of less sig- 
nificance. The formation of the Coast Ranges therefore has been a 
complex process spread over a considerable interval from the middle 
part of Miocene time to the middle of the Pleistocene, the compression 
increasing in severity and reaching its climax in the last deformation. 
Movements since the middle Pleistocene apparently have been pre- 
dominantly vertical, either upward or downward. 

The mid-Pleistocene folding accentuated Pliocene folds and faults 
and formed new structures of the same sort which deformed strata 
laid down both below sea level and above during later Pliocene and 
early Pleistocene time. 

The mid-Pleistocene uplift was rather rapid, greatly steepening the 
mountain fronts from which great and small masses of slide rock broke 
loose. That these slides occurred some time back is proved by the 
amount many of them have been eroded. At numerous places there 
are hills and ridges along the mountain fronts that are covered with 
slide debris derived from the scarp of the principal ridge behind the 
bordering hills. In some localities there is a sequence of slides with 
the later being sm'aller because of decrease in the slope of the moun- 
tains as erosion gradually subdued them. These huge jumbles of rock 
in many places completely hide the scarps, giving an erroneous im- 
pression of the distribution of the rock formations and structures. 

Along the coast and in the valleys there are many finely developed 
marine and river terraces shown to be later in origin than the mid- 
Pleistocene deformation because they commonly transgress structures 
formed at that time. The terraces testify to the spasmodic character 
of the uplift of the various blocks, having been evolved during episodes 
of quiescence and raised during times of increased intensity of defor- 
mation. In certain places there may be definite intervals between 
terraces, but farther along these intervals change, indicating differ- 
ence in rate of uplift which warped the terraces as they rose above 
the sea. 

Coastal terraces do not seem to correspond very closely with those 
developed along river valleys within the ranges, probably the result 
of more rapid uplift along the west side of the province since middle 
Pleistoc'iue time than has occurred farther east. 

( 137 ) 



IBull. 158 1»»2! 

^i^^vS " wax 1^ - j- 

■ -^ggisM 


^^^^^^^ Air Photos 





y 'w- 

'ide of CujBma Valley in San I.uis ( itispo i juri- . ' -'^ coalescence of st- 

borders the base of the mountains. Photo courtay Upeace A*r I'hotot. 

m\ fans 



[Bull. 158 

Flo. nii. Klevatcd wave-cut terrnco at Vmut Art'tui. I'huio hii (iliif F. ./t-jiAin.i 

Tlie liost kiiuwn ami jierluips tlie nujst iiiipiirtiint fiiult or I'il't 
system in the ('oust Kaiifies is tlie San An<lreas. In tlie central portion 
of the jirovince where this ;rreat fraeture zone has been most tlioroufihly 
stiulied, it lies elose to but not exaetly alonj; the eoiirse of a different 
type of fault formed in Eoeene time. What the relationships are in 
other plaees we do not know, exeept that in places it does transgress 
faults and folds developed durin;.' the middle Pleistoeene mountain 
buildiufr, and therefore is younprer than they are; it also fractures 
erosional and deformational features formed after the main deforma- 
tion. Nearly everywhere alon;; the San Andreas rift, evidence of recent 

Tilted .strata north of Pescadero Creek. Sea cliff and elevate<l terrace 
ill backftroand. Photo hy Olaf /*. Jenkins, 

. ll.'i. .V .~. 11.., of .stepped ilislocaliims iiiused by eartluiiiaUe iif I'.lOt;. as seen 
ill I'oad crossiiiK deep alluvial till near Salinas, Monterey Couilt.v. I'tiolo jrom ./. (\ 
Hronncr voUfftion, rourti'si/ Stiinford I' niversity. 

movement such as sa;; ponds (small depressions of limited area), small 
elevated blocks or buttes, offset ridfres and drainage lines may be seen, 
while there is no similar evidence aloiif: the mid-Pleistocene faults. 
At the time of the lOOfi eartliquake, open rifts showed in the (.'round 
aloii^r 270 miles of the fault north and south of San Francisco. 

Some freolofjists believe that p-reat horizontal dislocation lias taken 
place alonjj the San Andreas rift, most of the movement haviufr taken 
place in that direction, and that the oft'set is measurable in miles or 
scores of miles. Altho\ip;h the exact amount of dislocation is difficult 
to determine, it appears to be less than a mile. The maximum offset of 
drainage lines caused by the repeated breaks along the fault is about 
:3,000 feet. Thus, in spite of the 600-mile or more length of the rift, 




Fig. 1\G. GiKanttc earthflow south of Gilroy. Slides of masses of rock mantle and poorly cimsolidated n< 

is waterlogged and slippage easy. Photo by Clyde Sundrrlatid. (hikhmd. rnhiurni'i. 

■;ist Ranges Province when the ground 


I Bull, i:.- 

K.C. 117. I...w.r e,„l ,.f ™r,hH„w Jun.l.le .....r (iiln.y. sh,.w„„ Hu.ruH.ns.ic irn..ulaHy f,„e„M.e.l s„K„co. y*o,o ^. r,„,/c N ,cr,.u,„. OM..„l. CaUfonn,.. 









Fig. 118. Closer view of scar and earthflow jumble near tiilri>>. Vhoto by Clyde Sundeilnml, fhiklund. California. 



(Bull. 158 

it has had little influence on structure or toiioH-rapliy developed by the 
intense mid-Pleistocene fold-faultin?. at least in the central |)art of 
the Coast Ranges. 

Valleys eroded in llie crushed rock aloii"; the San Andreas rift are 
aniontr the youngest land forms in the province. 
San Francisco Bay Region 

The liills and mountains lyin^ west of San Francisco Bay are 
divided into a northern and a southern section by the Golden Gate: 
to the south is San Francisco peninsula; to the north is JIarin penin- 
sula with its crowninjjr point. Blount Tamalpais, whose two summits 
West Peak (2,604 feet) and East Peak (2.586 feet) may be seen for a 
lonjr di.stance. 

North of the Golden Gate and the bay, the Coast Kanfres consist of 
various ridfres oriented somewhat west of north. There is little agree- 
ment on the names of most of these rau<;es or the area to which the 
better recoprnized names apply. Between lie Petaluma or Sonoma. 
Napa, Clear Lake, and Berryessa valleys, named from west to east ; 
each is a ma,jor structural depression sharply contrasted with the 
lesser canyons and valleys carved into the raiifres by streams. About 
50 miles north of the bay. all but the Sonoma Kan^c merpe into a much 
dis.sected ui)land called the Mendocino Plateau which has an average 
elevation of 1,600 feet on the western side and 2.100 feet on the eastern 
where hifrher residual peaks of the Jlendocino Raufre are seen. The 
ni)land without question is a subdued erosion surface developed at 
lower elevation in past time, later raised, and now in process of 
destruction. Of the ma.ior structural depressions, only the Petaluma 
and its extension along the Russian River project as far north as the 
Mendocino Plateau. 

South of San Francisco Bay. the Santa Clara Valley, which is much 
larger than any on the northern side, .separates the Coast Ranges into 
an eastern division often called collectively the Diablo Range and a 
western termed the Santa Cruz Mountains. The Santa Clara Valley 
is the largest structural depression of the central section of the Coast 
Ranges, having a length of about 100 miles and a width of 15 miles 
where it is flooded by the .southern part of .San Francisco Bay. The 
lower 75 miles of this valley are drained by Coyote Creek into the bay ; 
whereas the upper 25 miles, isolated from the rest by a large alluvial 
fan, sends its waters first into Llago Creek and thence into the Pajaro 
River which empties into Jlonterey Bay. 

The Diablo Range, the mountainous belt of San Francisco Bay 
and south of the Sacramento River, is divided into several smaller 
northwest-trending ridges .separated by valleys largely controlled by 
prominent faidts. The highest peak in the northern part is the promi- 
nent Mount Diablo, of Walnut Creek, which rises :i.849 feet above 
sea level. South of the Livermore Valley, the Diablo Range, locally 
known as the Mount Hamilton Range, has a width of more than 30 

miles and some jieaks exceeding 4,000 feet high. The Berkeley Hills, 
immediately east of San Francisco Bay, considered by some as a unit 
distinct from the Diablo Range, form a moderately rugged belt about 
15 miles long and 10 miles wide with a prominent western-facing scarp. 
Between the main portion of the Berkeley Hills and the main portion 
of the Diablo Range lies San Ramon Valley, a structural depression. 

West of San Francisco Bay, the Santa Cruz Mountains exten<l for 
nearly 85 nnles scuithward from the (Jolden Gate to the Pa.jaro River. 
This section of the Coast Ranges is narrowest and lowest in the San 
Francisco Peinnsula. widens and grows higher beyoiul. but again 
narrows notably at its southern extremity. The highest peaks stand 
about 3.700 feet above sea level. Northwest-trending .structural val- 
leys are present in the Santa Cruz Mountains but are less conspicuous 
than in the Diablo Range. 

The crests of many of the Coast Ranges both north and south of San 
Francisco Bay are broad, rolling uplands. Peaks and ridges rise above 
the upland both in the south and the north. In the Santa Cruz Moun- 
tains two erosion surfaces are present, one at 600 feet and the other 
between 1.100 and 1,200 feet, but it is uncertain whether they are two 
distinct erosion levels or parts of one separated by faults. Elsewhere 
there is a single well advanced landscape now' being deeply trenched 
by young canyons cut because of the elevation of the ranges. 

The Santa •WiHH^ilouutains are separated into two parts by Merced 
Valley which runs westward from the bay to the ocean. On each side is 
a much eroded tilted fault block having a west-facing scarp and a gen- 
tle back slo]ic. The high |ioint nf the northern block is San Bruno 
Moinitain (1.315 feet), while that of the southern block is Montara 
Moinitain (1.052 feet). Separating the two blocks is the San Bruno 
fault lying at the base of the steep .southwestern front of San Bruno 

The northern block is irregularly hilly, and except in San Bruno 
Mountain, there is little parallelism between hills and valleys and 
the trend of the block. The topography is generally subdued though 
certain rugged areas of resistant chert stand out. Chert is a rock 
composed of almost pure silica. On the other hand, in the southern 
Montara section, crests and valleys run parallel to the long axis of 
the block and the topography is much more vigorous than in the San 
Bruno Hills. The most notable feattire of the Montara block is the 
valley containing San Andreas and ('rystal Springs lakes and through 
which runs a portion of the great San Andreas rift. This valley has 
been partly formed by earth movements along the fault b\it more 
important has been the easy erosion of badly crushed rock in the frac- 
ture zone. Northeast of this valley lies Buriburi Ridge which slopes to 
Merced Valley and San Francisco Bay. San Mateo Creek cuts trans- 
versely across this ridge draining the San Andreas rift valley and 
flowing through a narrow gorge to the Bay. 




Fig. 119. Sand dunes in a cove at Pi.snin 1 _- the Coast Ranges shore. The unsymmetrienl form of the dunes is clearl.v shown ; the gentle slope 

is in ttie dirtt-uon of the prevailing wincK I'holo t-cmrlesy Sitem-r Air I'hotos. 



I Hull. 138 


Vu-. IJ'i, Ml. a f;iillt l.l...k Ml |,;, \ xini.iur.' in iIh' Ci:!.! K;Mm.«, 

I'holo by hiirirf. Snrmnn /•,'. .1. Ilititls. HHnMllh'I'IIOIMdY ('r/j|iyii.//.( ;.'l J.i hi/ 
I'rrutiiT-lliill, Inc., AVir York). Ifeprodnred hi/ in'rmiH.tion of the puhliihrr. 

The slope of the Montai-;i block southwest of the rift valley is broken 
by a series of narrow canyons and ridges which are in lartre part rem- 
nants of the oriprinal erosion surface tilted upward as the block rose. 
Alonp the .southwest base of Montara Mountain but separated from it 
by an alluviated valley is a low riilsre known as Miraniontes which 
terminates oceanward in Pillar Point. 

The shorelines of the two sides of Ran Francisco Peninsula are 
markedly different. On the Pacific side viprorous wave attack apainst 
the momitaius has devehiped lon^ stretches of sea cliffs with .sandy 
or pebbly beaches at their base ; coves between headlands are well filled 
with sediments broufrht in by rivers, waves, and currents. There are 
only a few prominentl.v projecting' points like San Pedro. Off the head- 
lands stand rocky islands, like the Seal Rocks on the south side of 
the (lolden (iatc. which have been isolated by the wave attack and are 
}:raduall.v bein^' destroyed. In contrast the ba.v-side shoreline is highly 
irregular with tidal .marshes and other evidences of deposition in 
numerous bays between conspicuous promontories. Cliff erosion is 
feeble and there are no clean sand.v or pebbly beaches. The shore 
features on the bay side especially indicate rather recent submergence 
of a considerably eroded land mass. Similar submergence also is indi- 
cated along the oceanic side of San Francisco Peninsula, as for example 
at Lake Merced, which before it was modified for use as a reservoir, 
was a drowned valley cut off from the ocean by a bar of drifting sand. 
The Golden Gate is another illustration : there the ocean has invaded 
a young can.von which the Sacramento River had cut across the moun- 
tainous barrier. 

Sand dunes are abundant along the Pacific side of the Peninsula. 
The sand is brought to the ocean by streams or is prepared by the 
attack of waves on rocks along the shore line. Prevailing winds drift 
this debris for a considerable di.stance inland, forming dunes or scat- 
terings and irregular piles of sand called drifts. This encroachment 
has been largely checked in certain places by building of citj- improve- 
ments or planting vegetation. This was one of the prime purposes of 
the establishment of Golden Gate Park. 

Marin Peninsula, north of the Golden Gate, is a continuation of the 
mountainous .section to the .south and is separated from it by the nar- 
row channel through which the ocean has si)rea<l to fcrrm San Francisco 
Bay. The mouths of stream valleys descending to the ocean from the 
highlands have been embayed indicating either that the Peninsula has 
sunk or that the ocean, rising as the ice of the fourtli glacial stage 
melted, has invaded the lowest parts. From the highest point. Mount 
Tamalpais, a ridge extends west and northwest for a considerable 
distance. The slopes from the peaks and from the ridge are steep in 
all directions and are broken by deep gorges between which lie narrow 
ridges. However, where these can.vons approach the shoreline, the.v 
widen and their floors are flat, mostl.v salty marshes, a product of 
sedimentation in the emba.vments. This is notably true on the bay side 
of the peiunsula, where Tiburon Peninsula and San Quentin Point 
separate three main bays reaching far inland to the base of the moun- 
tains. Each of these indentations has a wide .sedimentary fill, the delta 
plain of the stream which carved the valley. On the western side of 
Mount Tamalpais, ridges and valleys either descend to the sea or to a 
long valley separating the peak from the Point Reyes Peninsula. 

Besides the Golden Gate, Elk Valley Marin Peninsula from 
the head of Richardson Bay to the head of Tennes.see Cove. This valley, 
while possessed of rather low bottom .slope, has steep walls and lies 
almost at right angles to the trend of the JIarin block. Its origin is not 
yet fully understood. The bottom is alluviated to some extent by wash 
from the walls. 

Point Reyes Peninsula is geographically distinct from the main part 
of Marin Peninsula to the east and is separated from it by a long 
narrow valley through which passes a section of the San Andreas rift. 
The north end of this valley has been submerged by the ocean forming 
Tomales Ba.v, while the south end terminates in Bolinas Lagoon which 
is separated from the sea by a wave-built saiu! spit. The formation of 
the valley, like a similar one previously described in the Montara fault 
block south of the Golden Gate, has been partly the result of earth 
movements along the great fault but more important has been the 
easy erosion of crushed rock along this fracture zone. The (piitc 
straight eastern margin of the Point Reyes Peninsula parallels and 
lies to this rift valle.v ; from the ridge along this eastern bound- 




Kio. 121. Coas( south of San Frnnoisoo. The relatively straicht shore line, prominent cliffs, fen- projeetine heatllanils. and clean, sanil.v lieaches are characteristic. Hich- 
land in the forcEround is the Montara block. To the north ore Merced Valley and the San Hruno block. In the ltuckj;ruund is Mt. Tainalpuis, high point on the ridge extentl* 
ing north of the <iolden Gale. Photo by Fairchild Aerial Suvveys. 



[Bull. 158 






[Bull. 158 

ary, the fri'iieral slope is fo«anI the ocean. Streams have ihaniieled 
the surface ami their lower ends have been drowned by invading 
sea water. 

At the south end of I'oint Reyes Peninsula is one of the finest wave- 
cut terraces alonir the California coast. The surface is ([uite even but 
does slope (rently upward from its outer margin to nuich eroded sea- 
eliffs whose base stands about 2.50 feet above the sea. The terrace is 
being dis.sected by small streams Mowing to the ocean from the higher 
land along the eastern side. Along the western side of tiie main part 
of Point Heyes Peninsula there is no comparable terrace, a fact for 
which we have no explanation. 

As with most of the Coast Ranges province, landscape evolution in 
the San Francisco Bay area has been complicated and is far from 
being perfectlyunderstood today. None the less many pertinent facts 
are known which give at some understanding of the history of 
this magnificent harbor which is matched in few places round about 
the worUl. The bay occupies part of a long valley lying between and 
almost completely enclosed by prominent hills, a setting which con- 
tributes to its beauty. Along the western shore, headlands and penin- 
sulas project into the water and are separated b,v canyons extending 
far into the hills. In contrast about 40 miles of the eastern side is 
bordered by a low plain which slopes gentl.v to the base of the Berkeley 
Hills; above the surface of this plain project a number of low hills 
and ridges. Islands like Angel, Verba Buena, Alcatraz, and Red Rock 
rise boldly above the bay surface. Treasure Island which extends north- 
ward from Verba Buena is an artificial construction used as the site 
of the Golden Gate International Exposition of 193!) and now of a 
great naval establishment. There also has been considerable addition 
to the land along both eastern and western shores of the bay by 
man-made fiUs. 

Most of San Francisco Ray is shallow, being less than 18 feet deep 
with 8.J per cent than 30 feet. There are, however, deep channels, 
courses of the principal streams flowing through the valley before it 
was submerged ; tidal flow has developed in these channels, a .sort of 
submarine stream system which keeps them swept relatively free from 
sediment. The greatest depth of water (381 feet) is in the main trunk 
channel through the Golden Gate, while in the main branch to the 
north. Racoon Strait, the maximum depth is 185 feet. 

During the middle Pleistocene mountain building large scale block 
faidting and other deformation occurred in the San Francisco Bay 
region roughly outlining the area later to be partly submerged by the 
ocean. It is po.ssible that the later and relatively mild deformation 
which produced the San .\ndreas rift and certain other features may 
have caused sufficient subsidence to allow the sea to enter the Golden 
Gate and spread farther iidand. The submergence was greater along 

the western than along the eastern side of the lowland, as the major 
flooding occurred there. The submergence was local ; the valleys of the 
Russian River 5(1 miles north of the bay and the Pajaro River 50 miles 
sotith were not drowned. Bolinas and Tomales bays were established 
along the San Andreas rift valley in Marin County, while Drakes Bay 
near Point Reyes seems to have been formed by the entrance of ocean 
water into the head of a valley system which drained southward towaiil 
the Golden Gate. Subsidence may have continued to the present, for a 
large shell mound on the east side of San Francisco Bay near Emery- 
ville stands more than 2 feet below sea level and similar situations 
exist elsewhere. However, another explanation of the ba.v 's origin nuist 
be considered. 

It is not definitely known when the drainage from the Great Valley 
began to reach the sea in the vicinity of San Francisco, but certainly 
there is no evidence of such a system prior to the late Pliocene defor- 
mation. Some have thoiight that the Sacramento River did not How 
to the Pacific Ocean through the Golden Gate h\it rather was directed 
southward through Santa Clara Valley to Monterey Bay. The pre- 
ponderance of evidence now at hand opposes the latter concept. 

The depression partly occupied by the bay has long been regarded 
as being primarily the product of deformation though it is also well 
known that its contour has been modified by erosion and deposition 
before the bay appeared. Early explanations called for the tilting of 
fault blocks along fracture zones, the eastern edge of the San Fran- 
eisco-Marin block lying against the base of the Berkeley Hills. But 
the Hayward fault, the great structural boundary at the western base 
of the Berkeley Hills, is not located where such a margin should be 
under the terms of the foregoing explanation. The boundary of the 
southern part of the bay had been thought to be the Montara block 
which was tilted up to the west along the San Bruno fault. Howcvi'r, 
it is difficidt to fit the distribution of land and topography into 
any definite adjustment of major fault blocks. The bay valley eros-ses 
supposed boundary faults on both sides and transgresses adjoining 
blocks. The valley at various angles over all medium to large 
faults in its vicinity and cuts across other structures both young and 
old. Only for limited distances does it follow one or the other. There- 
fore the most reasonable origin of the depressed area seems to be down- 
warping with some slopes formed by normal open folds while others 
are the product of faulting distributed along zones of various width.s. 

The elevation of the Berkeley Hills seems to have been a prime event 
in the evolution of the bay district and the first rise of this block at the 
time of the late Pliocene deformation may have coincided with the 
initiation of the depression now partially flooded by ocean water. 
During the middle Pleistocene mountain building, the re-elevation of 
the Berkeley Hills was slow enough so that the Sacramento River 




Flo. 124. Ycrlin Ituenii IsImimI i fiin-muiiii i . :ni cn.-hin r.-.,i,i i ~ ■, Krnncisco Bay; tip of San IViiiusula to left, in background. Marin liiU.- Ic ntlil. 

Kxleuding froDi the north o{ Verlia Huemt is TreaMire inland, an artificial construction now a naval hasc. Photo by Spvnve Air Photon. 



[Bull. 158 

maintained its course across them, eroding Carquinez Canyon, now 
Carquinez Strait, to a depth of 800 or 900 feet. Possiblj' simultaneous 
elevation occurred on the west side of the bay and at slow enoufrh rate 
so that the river kept its channel and cut Golden Gate Canyon, now 
Golden Gate Strait, to a depth of more than 700 feet. The lower course 
of the Russian River north of the bay and of Alameda Creek on the 
south side also seem to coincide with their position before the elevation 
of the ranges. On the other hand, most drainage was obstructed by 
the rise of ridges athwart their paths and the former stream courses 
are now represented by abandoned channels called wind gaps of which 
Racoon Pass, Liberty Gap, and Elk Valley are examples. 

A number of streams tributary to the Sacramento River before 
advent of the bay entered the main valley through open, V-shaped 
valleys whose bottoms are now 150 to 200 feet below sea level. Borings 
have shown that these streams were flowing on bedrock and therefore 
were downcutting instead of wandering over broad alluvial fills as they 
do today on their way to the bay. 

Most of the bay valley had considerably more diverse topography 
than the part immediately along the main river, being traversed by 
hills trending in directions somewhat diagonal to the main axis of the 
valley. Examples of these are the Potrero San Pablo west of Richmond, 
Coyote Hills west of Newark, San Mateo Point, and El Cerrito Hill. 
Other pronounced eminences are the various islands, while lower hills 
and ridges now submerged by ocean water have been revealed by 

Very late in earth history came the flooding of the canyons and 
associated lower parts of the valley region, developing the first stages 
of the drowned valley which was to expand into the present large-sized 
bay. Such emba\Tnents in many cases are the product of deformation, 
yet evidence has been obtained in the San Francisco Bay region show- 
ing that for some time prior to the invasion by the ocean, the rivers 
were actually eroding rising ground. This is particularly true north 
of the bay and along Carquinez Strait. 

We are now aware that many bays have been evolved by the rise as 
the great ice sheets and other glaciers of the last glacial stage melted 
or receded. However, in most cases it is not possible to tell whether all 
of the submergence resulted from increase in the volume of the ocean 
or whether deformation also played a part. Evolution of San Fran- 
cisco Bay bj' rise of sea level is consonant with much evidence which has 
been accumulated regarding the recency of its appearance, for the 
flood spread not only over the depressed area but also over some that 
was rising. 

The ocean first entered the mouth of Golden Gate Canyon which 
was being eroded in bedrock. Sea level has probably risen about 350 
feet since the beginning of the submergence. Most of the ice appears 

to have melted during the last 25,000 years of earth historj-, hence the 
main development of present-day San Francisco Bay must have 
(iccurred during that interval. 

The growth of the bay of course was slow. At first the streams 
retained their way to the ocean by way of the trunk channel through 
the Golden Gate, thougli tidal marshes gradually developed along 
their margins. As the ocean continued to rise, it drove the mouth of 
the Sacramento River back, progressively isolating tributary streams. 
Some hold that 10,000 or 15,000 years probably elapsed before Car- 
quinez Canyon was invaded and the ocean rolled into the lowlands of 
the Great Valley forming Suisun Bay, In fact the growth of the bay 
may have come very much clo.ser to o\ir time than the date just 

From recent studies of sea level changes during tlie last glacial 
stage, some authorities believe that the lowering of ocean level did not 
amount to more than 250 feet. If this is correct, the picture just drawn 
must be modified somewhat. The ba.v may have existed on sunken land 
prior to the beginning of the last glacial stage, then grew very much 
smaller as sea level fell, and finally assumed its existing dimensions 
as the ocean rose in exceedingly late geological time. 

With increase in the depths of the bay, it became a basin in which 
settled great volumes of sediment transported by the Sacramento River 
and its former tributaries. Advent of man to the region contributing 
sediment has greatly accelerated the rate of deposition, mostly from 
hydraulic mining, but also the result of ever increasing farming, over- 
grazing, improper lumbering, forest fires of human setting, and other 
activities. The great bulk of .sedimentation is at the north end of the 
bay, but the southern end also gets a considerable volume. Deltas have 
been constructed at many of the stream mouths and their inner parts 
have grown above .sea level as delta plains like those of Napa and 
Petaluma Creeks. Sedimentation is sufficiently rapid .so that the bay 
will be filled in a relatively short geological interval unless deforma- 
tion intervenes to deepen it. 

Beyond the Golden Gate and extending past the Farallon Islands 
lies the continental .shelf which is wider in this section than along most 
of the California coast. The shelf probably represents in part the delta 
of the Sacramento River when it flowed into the Pacific Ocean through 
the narrow gorge of the Golden Gate, but it has been added to by 
sediment carried from the bay during the flood season and dropped 
beyond this strait. 

Rising above the low plain bordering the west side of San Francisco 
Bay or from the ba.v it-self is the rather rugged, low, hilly block known 
as the Berkeley Hills. Some hold that this unit is part of the Diablo 
Range while others consider it a separate mass. The principal ridges 
in the Berkeley Hills are directed southeastward and the valleys be- 
tween them have been etched bv streams either into weak layers 



Fig. luri. U)w plain at base of Berkeley Hills. At the western base of the hills is the Ila.vward fault. Fholo by Spence Air Photos. 



[BuU. 158 

Flu. 12U. lii.>.T,ity of California, in tlie Bcrliele) Hills. The Hayward fault system lies 

s at base of the hills passing under stadium. I'liolo courtesy V . S. Army Mr Corps. 







m \ 

Kiti. 127. Mount St. Helena at the corner uf Napa. Souom:i. aixi 

iiuuiio, 1^ (.-'■lin" 

i-tiUil kolcaiiio ruck. Photo by i'lyde . 

>.i4...jnd, Calijornia. 



I Bull, ir 


between those more resistant or into crusheil rock alon^' faults. Tlie 
lii-;!] points on the main ridjies are Bahl Peak (l,!):iO feet), Grizzly 
I'eak (1,769 feet). Koiiiul Top (1,750 feet) and Redwood Peak (1,608 

The Berkeley Hills block is bounded on the southwest by a zone of 
intense deformation in which the principal feature is the active Hay- 
ward fault. It is quite certain that the zone of weakness considerably 
antedates in ori<;in the fault just referred to, a situation comparable 
to that found alonp part of the San Andreas rift. It is possible that the 
Ilayward and San Andreas systems join southward near Hollister, 
thoujrh this has not been positively demonstrated. 

Along: the Ilayward fault there are basins and buttes similar to 
tliose alonp: the San Andreas rift. One particularly well developed 
basin contains the southernmost jrreen of the Berkeley Country Club; 
this may be .seen just east of Ardmore Road whidi leads from Berkeley 
to Richmond. Perhaps the most striking feature alon<r the rift is a 
lonjr, narrow, interrupted valley between Claremont Creek and the 
vicinit.v of Ilayward. As the western scarp of the Berkeley Hills grew 
in height, consequent streams began to flow down it and carve young 
canyons ; this drainage is directed southwestward. Thus the valley fol- 
lowing the Hayward rift and paralleling the trend of the Berkeley 
Hills is out of accord with the normal trend of valley development. 
In tliis section between Claremont Creek and Ilayward, most of the 
drainage has been diverted for short distances along the rift valley 
before it returns to a normal southwesterly direction through breaches 
in the rift valley walls. The western slope drainage of the Berkeley 
Hills therefore appears to be older than the rift valley, where erosion 
has been made easy by the abundance of crushed rock developed as 
adjacent blocks have moved along the fault. Thus it appears that the 
Hayward fault is younger than the main fracture zone separating 
the Berkeley Hills and the San Prancisco-^Iarin blocks, just as the 
San Andreas fault is younger than that along which the San Francisco 
and Marin County and the Marin blocks are displaced. 

In addition to the Sacramento which held its course across the 
rising Berkeley Hills, another notable drainage feature was the deflec- 
tion into Alameda Creek of water which foniicrly flowed throu'ili 
Livermore, San Ramon and Ygnacio Valleys into Suisun Bay. This 
drainage alteration, an example of stream capture, explains the con- 
trast between the large San Ramon Valley and the small creek flow- 
ing through it. Alameda Creek flows through a deep, narrow canyon 
in the Berkeley Hills after receiving drainage from Mount Diablo 
and the Mount Hamilton range and flowing through broad valleys 
east of the Berkeley Hills. Its course between Sunol and Niles evi- 
dently was established before the elevation of the hills, whose rate of 
uplift was such that the stream was able to match it, eroding the 
canyon which it now occupies. Such streams, of w-hich the lower courses 



Vu:. V2H. Tn^Mch hi-iliK .iuf :il.i],;; ,1.:.. ,..,.11 ,|H.^(,l ,.r lulnl.i r.,rii|i,M I .•(! p.u-i- 
<'r fine rock fninincnts. As dike is relatively impernu'jilile. the water level on llie east 
(left) side stai)ds several feet hicher than on the west (ri^bt) side. Photo by Ala- 
meda County Wntt-r District. 

of the Sacramento and the Ru.ssian- River are examples, exist before 
the appearance of a mountain range, continue to flow across it through 
deep canyons, and thus are said to be antcccdiiit to the uplift. 

In excavations along the Hayward rift fragmented nick of the 
crushed zone has been exposed. Well illustrated at many places are 
the polished, scratched, and grooved surfaces produced by the grind- 
ing of rock masses against each other. 

This zone of deformation also is marked by a .series of step-faults 
which produce a terraced front in the hills like that particularly well 
shown between Strawberry and Cordonices Creeks. North of Cor- 
donices Creek such fatilts, although present, have had little effect on 
the topography. 

Many other faults are present in the Berkeley Hills but topographic 
features like those described along the Hayward rift do not show 
along most of them, indicating that they are of greater age. 

The structurally controlled ridges in the block have been abundantly 
•sculptured by streams so that there is a myriad of deep, young gorges 
trending roughly at right angles to the courses of the principal ridges. 
The ppasmodie nature of the elevation of the block is illustrated by a 
succession of river cut terraces in many of the canyons. 




Clinr Lake in Lake County is tlie larpest laiulslide lake in tlie state. 
The basin is a former plain 25 miles by 15 miles in size, which was 
drained by two outflowing streams. One of the streams, Cold Creek, 
had cut a deep gorge westward to the Russian River ; the other stream, 
Cache Creek, eroded a still deeper canyon through the range on the 
eastern side of the basin and eventually joined the Sacramento River. 
The eastern stream was later broken or had its course displaced near 
the entrance to its gorge by a .small lava How and the water was 
diverted into Cold Creek. 

Only a few centuries ago a large landslide, breaking loose from the 
middle part of the southern side of the western gorge, filled it up for 
a mile or more to a higher level than that of the surface of the lava 
flow on the other side of the basin. This dam backed up waters from 
the streams flowing into the Clear Lake basin until they finally over- 
flowed to the east through a sag in the lava flow at the mouth of Cache 
Creek canyon. The overflow cut Red Bank Gorge across the flow, re- 
established the drainage into Cache Creek canyon, and reduced the 
lake level about 60 feet. If this eastern outlet had not developed, the 
lake level would have risen until it overtopped the landslide barrier, 
which would probably have been eroded so that most or even all of 
the basin would have been drained. But because of the eastern outlet, 
surface rills and leakage through the slide can do it little damage on 
account of its great size. 

Since the early days of the lake, the narrow embayment that occu- 
pied the western gorge back of the landslide dam has been isolated 
from the maiii part by the broad delta of Middle Creek coming in 
from the north and has been further shortened by another delta, that 
of Scott Creek entering from the south. The remainder is divided into 
the two little Blue Lakes by combined delta plains of two wet-weather 

Clear Lake was artificially modified more than 30 years ago by con- 
struction of a 30-foot dam at the entrance to the eastern gorge and by 
blasting a rocky barrier to a slightly greater depth near the entrance 
of the eastern outlet stream through the lava barrier. This made 
possible the storing of a greater volume of water from the winter 
rains and of withdrawing it to lower than normal lake level for irri- 
gation of rice fields in the Yolo Basin of the Sacramento River during 
the summer time. As a result the lake level now usually stands a few 
feet above shore beaches formed before these alterations were made. 
However, the 25 to 30 inches of annual rainfall over the Clear Lake 
basin does not supply the inflowing streams with much more water 
than is lost by evaporation from the lake, hence the amount available 
for irrigation is small. 

Recent field work may alter to some e.xtcnt ideas concerning the 
parts played by the landslide and lava flow in the development of 
the lake. The study indicates that the deformation basin probably was 

of sufficient depth to have held a lake of some size had neither of the 
barriers been present and that it had been an area of sedimentary 
deposition for a long time, the debris being accumulated partly by 
rivers and partly in lakes. 

Volcanic Activity 

Pleistocene lava flows and volcanic cones are present around the 
southern margin of Clear Lake, largest natural body of water in the 
California Coast Ranges. Of the volcanic features Mount Konoeti, 
rising 2.800 feet above the lake, is most conspicuous. 

Muiiiit Konoctt is an eroded multiple volcano,- the highest part being 
south of the center of the mountain and including three prominent 
peaks, one of which apparently is the remnant of a secondary cone. 
About a mile north of this group Mount Buckingham, part of the 
volcano, stands at somewhat lower elevation and there are other small 
secondary peaks. 

In the visible part of the volcano, lava flows are most common, 
though fragmental deposits show on the lower western flanks and at 
other scattered areas. Konoeti therefore is a composite cone. 

There are remnants of several craters, the best example being 
Southern Peak, which has a shallow summit depression ; another, 
apparently larger example lies farther north and includes Howard 
Peak, highest point on the volcano. Small cinder cones dot the flanks 
as is so common in composite and shield volcanoes. 

The amount of erosion indicates considerable antiquity, the main 
activity having ended in middle or rather well back in late Pleistocene 
time. At the summit of Buckingham Peak, there is newer looking frag- 
mental material indicating possibly more recent eruptions from this 
northern summit. 

Southeast of Kelseyville on the western side of Clear Lake are 
several square miles of pumice-tuff and breccia which appear to be 
the oldest volcanics of Mount Konoeti. Most of the mountain, however, 
has been constructed from flows 50 to 60 feet thick; some tuffs and 
breccias are found between the lava flows. 

Lavas .south and of Mount Konoeti are similar to those com- 
posing the mountain and might appear to have come from it, but field 
evidence suggests that they actually were viscous flows erupted from 
a number of local vents. This is illustrated by Thurston Lake basin 
which is surrounded on all sides by steep lava walls that are the fronts 
of lava flows, the basin being formed because the flows coming from 
the various sides did not coalesce. Several small meadows in the .same 
area probably are filled lake basins formed in similar fashion. The 
elevation of Thurston Lake is about that of Clear Lake, but its level 
fluctuates considerably. The water is fresh in spite of lack of outlet 
apparently because of sufficient seepage through the lavas to prevent 
concentration of salts. It has been suggested that Thurston Lake may 
have been isolated from a larger Clear Lake by eruption of the flows. 



Bull. IJ-- 

r^^'^^f^'iK:^^^-^-:^ . 

Fic. 129. 

Mt. Konocti, a composite volcano neiir the southern end of Clenr Lake in Lake County. Mt. Konocti became extinct relatively late in geologic time. Clear Lake, 
iu foreground, occupies part of a structural depression in the northern Coast Ranges. Photo hn (\ \V. VheHicrman. 




Fig. 130. Sketch from aerial photograph across Clear I.ake toward the north- 
west, i. Thurston Lake basin ; i. lava field of Mt. Konocti : 3. Buckingham Peak, a 
portion of Mt. Konocti; .(. Little Borax 1.41 ke ; 5. Buckingham Peninsula: 6, High 
Valley: 7. Borax Lake. Sketch by C. A. Anderaon from photograph by Erickion. 

Beyond the area just described there are older flows of obsidian 
and other lavas coverinfr an area of about 12 square miles. Most of 
the flows are deeply weathered and the area is covered by dense chap- 
paral so that it is difficult to explore. These lavas also were apparently 
highly viscous when erupted as their huramocky surface forms indi- 
cate. The centers from which the flows came are unknown. 

Of much later agre are lava flows and cinder cones erupted since the 
development of the existing major features of tlie landscape. The age 
of the eruptions cannot be accurately determined, but lack of much 
weathering and erosion suggest that they have occurred in the last 
few thousand years. Precipitation in the region (about 30 inches 
annually ) has been enough to produce soil which supports a covering 
of chapparal and conifers. 

The best known of the recent volcanic areas is Sulphur Bank where 
solfataric ( hot gas) activity still goes on and has decomposed a recently 
erupted flow in part to white opal. Sulphur has been deposited at the 
same time, from oxidation of hydrogen sulphide gas as it escapes into 
the air. Mining of sulphur started about 1865, and at shallow depths, 
the mercuric sulphide, cinnabar, was later found ; from 1873 to 1945 
the area was intermittently mined for cinnabar, but hot water and 
gases interfered with underground operations. 

The lava at Sulphur Bank appears to have come from a vent under- 
lying the flow, which occupies an area of less than one square mile. 
The center of intense solfataric action is limited to the south-central 
part of the flow and may coincide with the vent from which the erup- 
tion came. Decomposition of the rock has been accomplished by 
sulphuric acid, formed by surface oxidation of hydrogen sulphide 
given off from the solfataras and hot springs. The decomposition has 
proceeded spheroidally, masses of fresh lava being surrounded by 
shells of opalized rock. Sulphur and more rarely cinnabar have been 
deposited in these shells. 

A mile or two northeast of Sulphur Bank, two cinder cones rise 
from an alluviated stream valley ; both have been breached on their 
western sides probably by explosion, for the cones have not been much 
eroded. The base of each volcano is about a mile in diameter and the 
the elevation close to 400 feet. Between the cones is a low ridge 
composed of lava fragments capped by a thin flow of basalt which 
apparently came from an opening between the cones. The fragments 
composing the little volcanoes have been more or less reddened by 

High Valley is an east-we-st depression several miles northwest of 
Sulphur Bank which has a length of about 3 miles and width of about 
a mile ; probably it is a small fault basin or graben which at one time 
may have been occupied by a lake, later drained by headward erosion 
of a tributary to Clear Lake. 

The eastern part of High Valley contains a recent flow of blockj' 
lava. A mile and a half east of this flow, a quite symmetrical cinder 
cone rises 400 feet above the lava field. In the top is a well preserved 
shallow crater about 300 feet across and 40 feet deep. The cone is old 
enough so that soil has developed in which some chapparal has taken 
root, but the slopes are almost undamaged by erosion. At the west 
base of the cone are two flows, one partly buried by fragments blasted 
from the volcano and the other later and not so covered. This lava field 
extends eastward as far as the North Fork of Cache Creek. 

There is evidence of recent volcanic action south of Borax Lake 
where an older flow is buried by a later outpouring which solidified as 
obsidian. The older body is rather thin with a front 15 to 25 feet high 
and is mostly made of blocky lava, though on the western edge the 
top is red and scoriaceous. The black obsidian above has a steep front 
40 to 50 feet high ; its top has broken up considerably so that frag- 
ments of the rock are interbedded in soil. It is possible that the open- 
ing from which the flow came lies in the northern part of the field, 
where there is a hill of pumiceous lava rising 30 to 40 feet above the 
obsidian surface suggesting that the last of the lava erupted was so 
viscous that it was elevated as a dome. 



(Bull. 158 

Koriix Lake occupies a shallow depression northwest of the obsidian 
flow. Occasionally it dries up. The source of the borax appears to be 
the northeast end of the obsidian flow where some solfatario action has 
recently occurred. Some sulphur is present but the obsidian is not 
badly decomposed. The solfataric action is now weak, though the 
ground is moist and warm and a faint odor of hydrogen sulphide 

The most southerly of the recent cinder cones surmounts recent 
flows less than a mile southeast of Thurston Lake. Like the Sulphur 
Bank cones it is breached, opening to the northeast. A flow of ba.salt 
extends to the east of the cone and probably is of later date. 

Chalk Moiiiildlii. east of the North Fork of Cache Creek, is a small 
conical hill about 400 feet high. The lava has been altered giving a 
brilliant white color which makes the hill a prominent landmark easily 
visible from the Williams-Clear Lake highway (No. 20), which runs 
4 miles to the south. Chalk Mountain apparently is a plug dome, exten- 
sively bleached and decomposed by later solfataric action. There is 
some discharge of cold water containing hydrogen sulphide on the 
western side of the dome, and the same gas can be detected at the top. 
Otherwise the vents are inactive. Stream terraces at the western base 
have been coated with white spring deposits testifying to the recency 
of the gas action. It is thought that the Chalk Mountain dome was 
elevated within the last few thousand years. 

Little Borax Lake occupies a shallow crater at the base of steep 
slopes descending from Buckingham Peak. This crater apparently 
was produced by a gaseous eruption without ejection of fresh lava for 
none of the fragments appears to have been liquid when blasted out. 

The water of the lake is saline and is said to deposit borate and 
carbonate minerals. Some lime deposits are above water level along 
the south side, but there is no hot spring action now. 

South of Mount Konocti are several isolated patches of basalt which 
have been partly eroded. They evidently were erupted after the devel- 
opment of the major landscape features in this section, but probabl.v 
are older than the other volcanic rocks belonging to the last cycle. 

Pinnacles National Monument 

Pinnacles National Monument is between Salinas and San Benito 
valleys in the Gabilan Mountains, a division of the California Coast 
Ranges. It is 35 miles south of HoUister and about an equal distance 
north of King City. The area, because of its remarkable topography, 
was set apart as a National Monument by President Theodore Roose- 
velt in IflO.s and lias been considerably added to since that time. The 
monument is most accessible from the eastern side by a branch of a 
road leading south from Hollister. Good trails have been constructed 
so that the principal scenic features are within reach of hikers. 

As the name suggests, the monument is an astonishing galaxy of 
rocky crags, spires, and pinnacles which make a most bizarre landscape. 

The area is not particularly high. Clialoue Valley has an elevation 
of about 1,000 feet, while nearby North Chalone Peak, highest point 
in the monument, stands •■3.2!I7 feet above sea level. Hawkins Peak, 
a spectacular assemblage of pinnacles, is more than 2,G00 feet high. 


25 5C 


Fig. 131. Map showing liK-atiou of Pinuacies Xational Monunu'lit. 
After Phillip Andretcg. 

Millions of years ago, this section of California was a vigorous 
volcanic field. Many lava flows were erupted and still greater thick- 
nesses of exploded products which were cemented together into vol- 
canic breccias. In the breccias the principal erosional features were 
sculptured after the rock had been broken by great numbers of prom- 
inent joints. Weathering along these fractures loosened fragments 
which have been removed by gravity and running water, perhaps a 
minor number by wind, thus enlarging the joints and evolving a weird 
complex of land forms. Deposition of silica from water migrating 
through the breccias has greatly hardened certain parts, allowing 
them to stand out from adjacent more easily erodable material. The 
lava flows also have been abundantly jointed in places so that the.v 
have behaved much like the fragmental deposits in the formation of 

Natural caves of rather large size are present along both branches 
of Chalone Creek, principal stream of the monument, which has under- 
cut beds of massive breccia. In scouring out less resistant material, the 




excavation has been so extensive in places that larpe, unsupported 
masses have slumped down. A short distance from the Pinnacles 
Ranger Station, a subterranean chamber nearly 100 feet across and 
in total darkness except when artificially illuminated, has been formed 
by a single block of massive breccia supported around the edges by 
smaller blocks. Large joint blocks also have rolled down the steep 
canyon slopes aiding the formation of the cavern.s. 

Except for Chalone Creek, streams flow through the monument 
only during and after heavy rains. The distinctly arid climate helps 
to preserve the angular outlines of the landscape and prevents the 
formation of a heav\' soil cover. 

Prior to the beginning of the volcanic episode, long erosion had 
reduced this section of California to a lowland of very subdued relief 
etched in various kinds of rocks with granite being the chief type in 
the monument. The resistant granite basement was broken by nu- 
merous fractures probably during a later deformation and along these 
rose masses of rhyolitic magma which solidified as sills and dikes, some 
of which were undoubtedly feeders for the flows poured out on the 
surface. The earliest surface eruptions were rhyolite flows which piled 
one upon another in considerable thickness, though somewhat later 
andesitic and basaltic magmas also were poured out. In the last stages 
of this flow episode, the lava apparently became quite viscous and a 
large, steep-sided mass was elevated along one of the fractures form- 
ing a volcanic dome having an elongate pattern contrasting with the 
more or less nearly circular examples in Lassen Volcanic National 
Park, Mount Shasta, and the Mono Cones on the east side of the 
Sierra Nevada. 

Then from five nearly circular vents and possibly more, explosive 
eruptions blasted out great quantities of solid and liquid fragments. 
The largest center was that of South Chalone ; the others definitely 
known follow a roughly north trend. The centers can be identified 
because explosions filled them with layered masses of rhyolitic tuff 
while round about is massive rhyolite. In these vent-fillings, as they 
are called, conical pinnacles have been carved by erosion. 

The eruptions occurred during Miocene time, the third epoch of the 
Cenozoic era, consequently much evidence regarding them has been 
destroyed by erosion. Probably the massive breccia deposits were 
formed by several agencies including various types of violent vol- 
canic explosion and the crumbling of the walls of the steep rhyolitic 
dome which formed a deep mantle of talus. Many flows followed 

explosive eruptions, enveloping great quantities of fragments and 
cementing them together. Other flows broke into brecciated masses as 
they advanced. Avalanches and the natural angles of repose of this 
coarse material maintained the steep slopes of the dome ridge. 

The length of the volcanic episode cannot be estimated, but it must 
have been long, as more than 4,500 feet of fragmental debris is left 
and in addition a considerable thickness of lava flows. In addition, 
both explosive and flow eruptions were repeated after interruptions 
of various lengths during which volcanic activity virtually ceased and 
weathering and erosion of the volcanic deposits took place. 

Faulting that occurred after the close of the volcanic cycle displaced 
rocks along the fractures considerably. Three principal faults are 
present in the Pinnacles National Monument, all of them being roughly 
parallel to the San Andreas fault which lies a few miles to the west. 
Erosion has removed volcanic rock from areas elevated along the 
fractures so that the original extent of the deposits cannot be deter- 
mined, but it certainly has been considerably reduced. In quite late 
time the elevation of the region has caused conspicuous erosion by 
invigorated drainage. 


Anderson, C. A., Volcanic history of the Clear Lake area ; Geol. Soc. America 
Bull., vol. 47. pp. 627-664, 1936. 

Andrews, Phillip, Geology of the Pinnacles National Monument : Univ. Cali- 
fornia Dept. Geol. Sci. Bull., vol. 24. pp. 1-38, 1936. 

Davis, W. M., The lakes of California: California Div. Mines Rept. 20, pp. 
175-236, 1933. 

Howard, A. D., Development of the landscape of the San Francisco Bay counties ; 
California Div. .Mine.s Hull. l.">4, pp. SrilOO. I'.l.'il. 

Lawson, A. C, The geology of Carmelo Bay ; Univ. California Dept. Geol. Sci. 
Bull., vol. 1, pp. 1-59, 1893. 

Lawson, A. C, U. S. Gcol. Survey Geol. Atlas, San Francisco folio (no. 193), 

Lawson, A. C, and Palache, Charles, The Berkeley Hills, a detail of Coast 
Range geology : Univ. California Dept. Geol. Sci. Bull., vol. 2, pp. 348-450, 1902. 

Louderback, G. D., Characteristics of active faults in the central Coast Ranges 
of California with application to the safety of dams : Seismol. Soc. America Bull., 
vol. 27, pp. 1-27, 1937. 

Louderback, G. D., Geologic history of San Francisco Bav : California Div. Mines 
Bull. 154, pp. 7.5-94, 1951. 

^Taliaferro, X. L.. Geologic history and structure of the central Coast Ranges of 
California: California Div. Mines Bull. 118, pp. 119-16:!, 1943. 

Weaver, C. E., Geology and mineral deposits of an area north of San Francisco 
^j, California : California Div. Mines Bull. 149, 1949. 



Within the Transverse Ranges, an east-west system in southern 
Ciiliforiiia. is a structural depression extendinp eastward from the 
coast and reaching south of the Mexican border. The basin is the most 
heavily populated section of California containing such cities as Los 
Angeles, Long Beach, San Diego, Pasadena, San Bernardino, River- 
side, Redlands, and many others. It is a great agricultural region and 
is becoming increasingly industrialized. The Transverse Ranges con- 
sist of the Santa Ynez and other low mountain groups and intervening 
valleys such as the Ojai and that of the Ventura River and the Santa 
Monica Mountains farther south which extend from Los Angeles to 
the coast. Separated structurally but a part of the transverse system 
and undoubtedly once connected with it above sea level are the Channel 
Islands — Anacapa, which has been .set apart as a National Monument — 
Santa Cruz, Santa Rosa, and San Miguel, named in order from east 
to west. Farther east and rising very abruptly above the plains are the 
San Gabriel Mountains which extend as far as Cajon Pass where the 
San Bernardino Range, the second high member of the Transverse 
system starts. The southern front of the San Gabriel Mountains forms 
the northern boundary of San Fernando, San Gabriel, and Santa Ana 
valleys, all of which lie to the west of Cajon Pass. 

The Vottura district, about 70 miles northwest of Los Angeles, is 
chiefly hilly and mountainous. It is comprised of a number of sections, 
the highlands being the Santa Ynez Range, an east-west trending 
chain on the north side ; the Sulphur Mountain Upland, a discon- 
tinuous highland in the central part formed by Sulphur, Red, and 
Rincon mountains ; and the Coastal Hills, a low hilly region adjacent 
to the coast and extending inland parallel to the Santa Clara River 
east of Santa Paula. The chief lowlands are the Ojai Basin between 
the Santa Yn^z Mountains and the Sulphur Mountain Upland, the 
Ventura River Valley, and the Santa Clara Valley along the south 
boundary of the district. 

In the area is a nearly complete record of Cenozoic history of coastal 
southern California, for an immense thickness of deposits, about 
47,000 feet, were accumulated partly when the land lay below sea 
level and partly when it stood above. The latest of the sediments belong 
to the uppermost Pleistocene, the earliest go back to the Eocene. Dur- 
ing the middle part of Pleistocene time, the entire mass was folded 
and faulted, then was beveled off with the evolution of a rather ad- 
vanced landscape. Still later, differential vertical uplift has invigo- 
rated the streams, developing the present erosion c.vcle. 

The older landscape, best preserved on the summit of Sulphur 
Mountain, is called the Sulphur Mountain erosion surface. It was 
characterized by broad valleys with hills and low mountains rising 

above. Because in places later erosion has destroyed this land- 
scape, its character has to be inferred from such remnants as are left. 

Part of the present drainage pattern of the district is inherited 
from the Sulphur Mountain cycle, but part is recently initiated. Most 
of the recent changes have been accomplished by licadward erosion 
and by diversion or capture of east-west streams by .soutliward flowing 
streams. As a result, a few large through-flowing streams have courses 
roughly at right angles to the fold and fault trends of the area. 

This east-west range rises about fi.OOO feet, making a prominent 
barrier along the north side of the Ventura di.strict. The streams of 
the southern part of this range are tributary to the Ventura River or 
to Santa Paula Creek. They flow down steep grades and have incised 
deep, narrow gorges into the mountain flanks. Since these principal 
tributaries flow nearly at right angles to the trend of the folds and 
faults, minor branches have excavated valleys into the weaker beds 
and hence parallel the structural trends. These lesser streams, having 
reached maturity, broadened their valleys and developed an almost 
continuous lowland paralleling the front of the Santa Ynez Mountains. 
This lowland, eroded in shale between two resistant sandstone ridges, 
shows prominently north of Ojai Valley and west of the Ventura 
River in Kennedy Canyon. 

The Ojai lowland is divisible into three parts, the Santa Ana Valle.v 
or western section, Long Valley in the center, and the eastern part 
which does not have a name. Tlie Santa Ana Valley is principally a 
bedrock surface covered with thin residual soil, while in Long Valley, 
this bedrock is covered by river terraces. The eastern part of the Ojai 
lowland is filled with alluvium and at the eastern end are the two large 
alluvial fans of Sennor and Horn Canyons. 

In the Santa Ana section, the two principal streams are Santa Ana 
and Coyote Creeks. The Santa Ana may have been inherited from the 
Sulphur Mountain erosion cycle, but its present valley was started 
during the period of uplift initiating the late erosion cycle during 
which the Sulphur Mountain surface has been largely cut to pieces. 
In an epoch of relative stability in the later cycle, the stream broadened 
its valley by the erosion of a wide terrace and then incised a narrow 
arroyo 50 feet deep below the terrace in consequence of a very recent 
uplift invigorating the power of the stream. 

Coyote Creek was established later than Santa Ana Creek by head- 
ward erosion and diversion of east-flowing tributaries of the Santa 
Ana drainage. 

East of Santa Ana Creek, the history of the valley is uncertain. The 
valley is divided into two nearly equal sections by a low ridge crossed 
both by Santa Ana and Coyote Creeks. The two halves of the valley 

( 185) 



[Bull. 158 

in the area east of the Santa Ana Creek may have been excavated by 
tributaries of the Ventura River when it flowed at a considerably 
higher level than at present. 

The upper Ojai Valley is a small, lens-shaped basin about 5 miles 
long and 1 mile wide, ranging in altitude from 1,250 feet at the west 
to 1,550 feet at the and separated from the main part of Ojai 
Valley by a ridge 50 to 150 feet high at the southern end and 300 to 500 
feet high farther north. Westward the same ridge rises to 1,035 feet 
at Lion Mountain. The difference in elevation between the two parts 
of Ojai Valley probably results from erosion by San Antonio Creek 
along the eastern part of the Santa Ana fault which crosses the 
northern base of the dividing ridge. Because the south side of the 
fault has moved upward bringing resistant and less resistant rocks in 
contact, erosion has been slower on the southern, more resistant side, 
which now stands higher. 

This nearly continuous ridge, convex to the south, runs through 
the center of the Ventura district and is breached by only two streams, 
the Ventura River and Santa Paula Creek. It consists of Sulphur 
Mountain east of the Ventura River and Red and Rincon mountains 
to the west. 

The conspicuous feature of Sulphur Mountain is the sharp contrast 
between the advanced mature landscape of the summit, the elevated 
erosion surface of earlier time, and the bold southern face. Some have 
interpreted this declivity as a fault scarp, but actually it has been 
evolved by rapid stream removal of easily eroded shale. 

Red Mountain, west of the Ventura River, is an elongate dome. 
In the weak rocks exposed during erosion of the dome, valleys have 
been evolved parallel to the structure and are separated by ridges of 
more resistant strata. These valleys are tributary to the drainage flow- 
ing down the slopes of the dome. Such a circular or elliptical valley 
and ridge pattern is often called race-track or annular topography. 

On the summit of Red Mountain are numerous undrained depres- 
sions formed by movement of masses of sandstone down the slope. The 
hollows range from 100 to 400 feet long and 20 to 60 feet deep. Many 
contain permanent ponds while others are partly filled or converted 
to grassy flats. Most of the undrained hollows are at the east end of 
the mountain north of a large, now inactive slide at the head of Canada 
del Diablo. A large slide in Padre Juan Canyon has projected the 
amphitheater-shaped head of this valley through the original crest, 
so that its stream is now attacking the north side of the mountain 
where it has beheaded several northward flowing streams. 

As is common, the slide blocks have rotated backward as they have 
moved, and the undrained depressions lie between the rotated blocks 
and the scar left on the hillside as the masses broke away. 

Rincon Mountain resembles Sulphur Mountain in its general topo- 
graphic form and much of its geology. The crest is a rounded ridge 
falling off abruptly to the north and south, but rising gradually east- 
ward to the domelike summit overlooking Los Sauces Creek. This 
rounded crest is a remnant of the Sulphur Mountain erosion surface 
and is the most prominent feature in the coastal area, standing 2.165 
feet above sea level. On the south side of Rincon Mountain are 9 levels 
of marine terraces, the highest being between 1.250 and 1,300 feet 
above sea level. The terraces have been warped in process of elevation 
and increase in altitude ea.stward. All of the terrace surfaces are buried 
by later detritus which obscures a thin layer of older fossiliferous 
marine sand and gravel overlying wave-cut platform. 

The Coastal Hills include the area between Sulphur Mountain and 
the Santa Clara Valley and inland from the coast to the eastern 
boundary of the region. The hills range in elevation from 1.000 to 1.950 
feet. Tlie Sulphur Mountain erosion surface undoubtedly extended 
across this section, but has been almost completely destroyed, being 
replaced by a hill and valley topography. 

Landslides are abundant and even more so are masses of debris 
called earthflows that were water-logged when they started to slide. 
The landslides have moved down favorable surfaces of resistant strata 
while earthflows have occurred generally throughout the hilly belt. 

The Ventura River flows from the Santa Ynez Mountains for 12 
miles before entering the Pacific Ocean a mile west of the city of 
Ventura. It has a narrow flood plain in no place reaching a mile in 
width and in few places more than half a mile. In the lower part of 
its course the river meanders slightly, but in most places has an 
anastomosing channel, especially north of Ojai Valley. The last 2 
miles of the valley seem to be underlain by deep alluvium, indicating 
that there was excavation in this section probably when the sea stood 
lower during the glacial stages of Pleistocene time. 

Along the Ventura River are terraces which provide important 
information regarding the extent and nature of deformation since 
erosion of the Sulphur Mountain surface. The highest terrace stands 
at 1,180 feet on the west end of Sulphur Mountain where it merges 
with the Sulphur Mountain erosion surface, indicating that the Ven- 
tura River had evolved before the late Pleistocene uplift while the 
erosion of Sulphur Mountain surface was going on. The river prob- 
ably established its course by headward growth and capture of an 
earlier drainage system, much as Santa Paula Creek has done in divert- 
ing west-flowing drainage of the upper Ojai Valley. 

Deepening of the Ventura Valley kept pace with uplift, going on 
most actively when elevation was most vigorous. Then during episodes 
of greater stability, the valley widened out by the development of a 
lower terrace. This process has been repeated giving a succession of 




terraces. As the deformation progressed, the terraces were bent into 
a broad arch which reached its maximum elevation at the Red Moun- 
tain fault. 

Marine Terraces 

At the base of the modern sea cliffs along the coast, there is a low 
wave-cut platform. Elevated terraces are restricted to two sections, 
I lie fii-st extending from Pitas Point 7 miles west to the Carpinteria 
Plain and the second from Ventura east to the Santa Clara River. 
West of Pitas Point, terraces are prominent and best developed on 
Hincon Mountain where they have been recognized as high as 1,300 
feet above sea level. Elsewhere their number and altitude are difficult 
to ascertain. Near Rincon Mountain the terraces have been tilted so 
that they slope toward the Carpinteria Plain ; almost all of them have 
I'lTii t-ut by faults wl'.icli prcdrce small offsets in their surfaces, these 
reaching a maximum of about 30 feet. 

Fig. 132. Wave-cut terraces covered by veneer of marine deposits and then 
buried or partially buried by nonmarine cover of .sediment after elevation of the 
terraces. A, Nonmarine cover concealing cliff between successive terraces. B, Non- 
marine cover over terraces but not concealine cliff between them. After U. S. Oeolog- 
icat Survey. 

Behind Ventura, marine terraces have been eroded but are difficult 
to recognize because the bedrock and the terrace gravels are quite 
similar. Terrace form is best preserved on the lower ones and virtually 
disappears above 500 feet ; evidence for their presence above this 
elevation is principally gravel remnants which may or may not be 
correctly identified as having been formed on a wave-cut surface. 
The best preserved terraces near Ventura are on the ridge immediately 
east of the Ventura flood plain. Practically the entire business district 

of Ventura is built on the lowest one which stands 15 to 20 feet above 
the ocean and measures about 2,100 feet wide. Eight feet above sea 
level there is a second conspicuous bench at the east margin of the 
Ventura River Valley, but farther east this and the lower one are 
largely buried by an alluvial fan which has formed at the mouth of 
the first canyon west of Hall Canyon. 

At 350 or 400 feet above .sea level is ihe flattened ridge, also a marine 
terrace, on which stands the Serra Cross. Between this and a lower 
terrace at 200 feet, conspicuously shown near a large excavation behind 
the Ventura County Courthouse, are four minor ones indicating that 
the emergence of the land was broken by intervals of relative stability, 
some longer, as that when the main terraces were cut, and others 
shorter, such as those responsible for the lesser notches. As the land was 
elevated, there was some fracturing with displacements of a few feet 
showing in some of the terraces. 

The evolution of the present shore line has been controlled by the 
direction of prevailing winds and currents and by inequalities in the 
resistance of rocks under attack by the waves. The unsymmetrical 
major headlands have a long northern side and are separated by short 
northeast-trending embayments. The sea breezes are generally strong- 
est in the summer when the Santa Clara and Ventura valleys connect 
highly heated inland with the coast. Ocean currents flow eastward as a 
result ; the waves associated with them parallel the longer stretches of 
the beach and approach the shorter side of each headland obliquely, 
the angle between the headland shore and wave front being between 
20 and 30 degrees. Active erosion goes on along those parts of the shore 
attacked by this oblique wave approach. 

Between Rincon Point and the Ventura River, the beach is a thin 
veneer of sand with bedrock cropping out for considerable distances. 
The widest beach is at Picrpont Bay southeast of the Ventura River, 
a shallow embai,Tnent between the Ventura and Santa Clara Rivers 
supplied with sand principally by the Ventura River. The beach is 
not being built outward, the shoreline in places standing as much as 
2,500 feet from the base of the seadiffs, a result of the northward 
migration of the Santa Clara River over its flood and delta plain. 

The last event in the history of this section of the coast has been 
slight emergence, shown by a wave-cut terrace exposed along the 
highway north of Pitas Point, where it stands 15 to 16 feet above 
sea level ; this increases to 21 feet a mile and a half southeast of Seadiff 
station showing that tilting has occurred during emergence. Projec- 
tion of the terrace landward beneath the cover of non-marine debris 
deposited on it indicates an elevation of about 45 feet at the base of 
the former sea cliffs which are 115 to 120 feet high. The terrace rem- 
nant is about 300 feet across at Pitas Point but increases to 1,200 feet 
at Seacliff station. 




[Bull. 158 


Flo. 133. The San Oaliriel Mountains near San Diuias. I'hoto by Spence Air Photos. 




The San Oahriel and San Bernardino Mountains are of about equal 
size and form an imposinfr barrier extending many miles north and 
east of Pasadena and Glendale. Both ranges are composed of a series 
of faulted blocks thrust upward from a region of rather low relief 
and elevated to their present height during Pleistocene time. 

The southern front of the San Gabriel Range is a bold, considerably 
dissected slope marked by a complex sj^stem of faults whose base forms 
a sharp but irregular line separating the low alluvial plain to the south 
from the mountain block. West of San Antonio Canyon near Clare- 
mont and south of east-west Tujunga and San Gabriel Canyons, the 
summits of the range are from 3.000 to 6.000 feet in elevation, while 
north of this area, they rise to 8.000 and 10,000 feet, the highest point 
being Mount San Antonio or Old Baldy (10.080 feet). The ridges of 
this portion of the Transverse Ranges are sharp and the canyons deep, 
hence there are few remnants of the advanced landscape which was 
elevated as this fault block rose. 

Like the San Gabriel, the San Bernardino Mountains are about 60 
miles long in an east-west direction; they widen from a point at the 
summit of Cajon Pass (elevation 4,250 feet) to nearly 30 miles at their 
eastern end. The crest line of the western section is remarkably even 
and forms the drainage divide between the Mojave desert, which is 
part of the Basin-and-Range Pro\-ince, and the coast. The crest begins 
near the summit of Cajon Pass at an elevation of about 5,000 feet and 
rises gradually for about 25 miles to the southeast where it reaches 
7.500 feet above sea level. Then it is broken by Bear Creek Canyon. 
Beyond this narrow gorge, which is more than 3,000 feet deep, the 
crest again rises for more than 12 miles to 9.500 feet, but is no longer 
the drainage divide ; it culminates in Sugarloaf Mountain, 9,500 feet 
high. Southeast of the Santa Ana River into which Bear Creek empties, 
the range is most rugged and reaches its highest elevation, with San 
Gorgonio Peak, 11,485 feet above sea level, as its supreme summit. 

In the vicinity of San Bernardino, the south front of the San Ber- 
nardino Mountains is a steep, battered fault scarp that faces the Santa 
Ana valley and makes a clearly defined straight boundary with this 
alluvial plain. 

The summit region to the north of the crestline referred to above is 
a gently rolling plateau whose high points do not rise more than 1,500 
feet above the bottoms of the valleys between them. The plateau is a 
remnant of the same advanced erosion surface that is much more 
damaged by later erosion in the San Gabriel Mountains. Prior to the 
uplift of these blocks, this flat surface seems to have occupied a large 
part of southern California, though its limits cannot be determined 
because of the great amount of later deformation. The features of this 
older topography in the San Bernardino Mountains are sharply con- 
trasted with the much more rugged topography developed as the range 

has been rising. This new landscape consists of deep narrow canyons 
which are eating headward into the plateau and gradually destroying 
it. Between the recently cut gorges are sharp crested, narrow ridges. 
The western part of the plateau drains into the Mojave River and the 
eastern part into the Santa Ana River. 

There appear to be two principal fracture belts on the southern side 
of the San Gabriel section along which this mass has risen, one lying 
at the foot of the range and the other somewhat farther back within it. 
The fault system along the front of the mountains is called the Sierra 
Madre ; the total displacement which has occurred along this fracture 
zone is probably about 5,000 feet, judging by the position of the bed- 
rock floor at the base of the range and the elevation at the top of the 
scarp. East of Dalton Canyon, this fault zone diverges from the range 
front and runs along the base of foothills south of the main scarp ; this 
section is called the Cucamonga fault, along which displacement 
ranges from a few feet to 1,000 feet west of San Antonio Canyon. 

The fault zone within the range is called the San Gabriel ; north of it. 
the range rises in elevation nearly 3.000 feet, a change that may be due 
to movements along the fault. 

Other fractures that have caused less displacement include the San 
Andreas, which cuts the San Gabriel Range near its northeast margin, 
and has moved horizontally. 

Most of the southwest margin of the San Bernardino Mountains is 
bounded by the great San Andreas fault, the major fracture system 
in California. The several faults that diverge from the San Andreas 
zone, swinging eastward into the range, are probably responsible for 
most of the uplift along the south and west sides. The western San 
Bernardino Mountains appear to be a succession of fault blocks, each 
tilted to the north. 

North of the San Andreas zone, five important faults run eastward 
into the range and appear to have been the zones along which the 
southwestern part of the mass has been elevated. 

The cumulative effect of the uplift which has taken place along the faults in the San Bernardino Mountains is partly offset by 
the tilting of the blocks northward as they have risen. However, the 
old erosion surface, represented by the even crest line, is 5.000 to 7,000 
feet above the bedrock south of the San Andreas fault where the same 
surface shows. 

The Santa Monica Mountains that start about 5 miles northwest of 
the City of Los Angeles and the four Santa Barbara Islands — Anacapa, 
Santa Cruz. Santa Rosa, and San Miguel — in the not very distant past 
were a continuous chain. The islands which are smaller units have 
been isolated by erustal movements while the main mass, the Santa 
Monica Mountains, is locked to the land by the Ventura Basin which 


[Bull. 158 

•^i'W- w<^''J %W- ■■/■■■'■■ wV-i' . ^^ 

v> f--t - --■ --" 

Fio. 1S4. 

^ ■ ■ ^^'*^ '™~*' *' ■ „ barrenness of the slopes „llows speedy rnnoff of heavy rains and conse- 

Oeep. narrow canyons "o-U . .,.e_Sa„ Ua.r.;^— ...s^^^ ,. ,. ,,„„ ,, .„.,,. 




Kni. l-'t.*. San GorKOiiio Penk, hijcli puint i 11.4.Vi f.-t-t i m tUv San Bernardino Range, a member of the Transverse prou|). Uivers have cut deep canyons into the ranfje. 
pxteasively deMroying an erosion surface of relatively gentle relief which extended across the mountain block prior to its uplift. Photo by Fairchild Aerial Surveys. 



[Bull. 158 

Fio. 136. 

Santa Monica Mountains (background), the slightly dissected Santa Monica alluvial plain (foreground), and sea cliflfs now being cut into 

the plain (left foreground) . Photo by S pence Air Photos. 




abuts against them on the northern side. Several kinds of evidence, 
partii-ularly elephant remains in Pleistocene rocks on the Santa Bar- 
bara Islands comparable with types found in rocks of the same ajre on 
the mainland, indicate stronply that the chain was formerly con- 
nected. The islands, an east-trending group, are now separated by 
deep submarine troughs, a plan characteristic of the rather broad 
continental shelf off.-ihore from the Los Angeles Basin. Studies sug- 
gest that the varied contour of the .shelf in this section, which con- 
trasts with the normal rather smooth seaward slope, has resulted from 
faulting which developed a number of small, nearly rectangular blocks 
which have moved upward and downward, giving a rather hetero- 
geneous arrangement of islands, submarine basins, and higher stand- 
ing underwater areas. This faulting is assigned to the late part of 
Pleistocene time. 

The Santa ilonica Range is about 45 miles long, has an average 
width of 10 to 15 miles, and rises from 1.000 to .3.000 feet above sea 
level, the higher parts being in the western section. The western 30 
miles front on the Pacific Ocean, where strong wave erosion has 
developed a prominent sea cliff 175 to "200 feet high. Highway 101 
runs along the base of this cliff and Highway 27 crosses the mountains 
from Topanga Beach west of Santa Jlonica. 

The eastern part of the Santa Monica Mountains has quite sub- 
dued contours, making them a hilly rather than a mountainous belt. 
The crests of the hills rise 1.300 to 2.100 feet above sea level or 800 to 
1,.')00 feet above the adjacent plains. There is some increase in eleva- 
tion westward. The crest of the mountains is a series of flat-toppeil 
ridges of about the same elevation. The Hat tops appear to be remnants 
of an old erosion surface which transgressed the iliocene strata of the 
earlier Santa Monica anticline. This advanced landscape, probably 
belonging to old age of the erosion cycle, seems to have been developed 
in the earlier part of Pleistocene time after a vigorous deformation in 
the later part of the Pliocene epoch. During the later part of the 
Pleistocene, the surface has been brought to its present elevation and 
has been materially dis.sected by streams. 

Some of the streams, like those in Topanga and other major .south- 
ward directetl canyons, are fed by springs and therefore permanent : 
the rest flow only during the heavier rains. The Los Angeles River, 
major stream of the area, flows from the Simi Hills and Santa Susana 
Mountains across the San Fernando Valley and around the eastern 
end of the Santa Monica Mountains. Generally drj-, the drainage sys- 
tem often carries wild torrents during heavy rains. 

The main drainage divide of the Santa Monica Mountains lies near 
the northern side and not in the central part as might be expected. 
This very likely results from the higher elevation of the plain to the 
north against the base of the mountains and the longer distance which 
the streams must flow to reach their lowest level of erosion. 

Although the Santa Monica Mountains, particularly the ea.stern part, 
are relatively subdued in contour and remarkably uniform in eleva- 
tion over considerable areas, yet there are some higher and more 
abrupt topographic features which appear to have been cau.sed by 
late faulting. The Vicente Mountain area west of upper .Sepulvetia 
Canyon and a wedge-shaped, fault-boundeil granite mass west of 
upper Laurel Canyon are examples. It also seems probable that the 
steep granite front of the mountains north and west of Hollywo<xl 
has resulted from comparatively recent movements along the Holly- 
wood fault, which were terminated on the west at the north end of 
the Newport-Inglewood uplift near Beverly Hills. Farther west this 
deformation was not by faulting but by uplift and tilting of a wide 
Pleistocene alluvial plain. Except for local faulting, the .Santa Monica 
Mountains seem to have been elevated as a unit in the late part of the 
Pleistocene epoch. 

The alluvial plain just mentioned is calletl the Santa Monica Plain ; 
it lies north of the city of Santa Monica and extends east and west 
along the of the mountains. The plain was formed by streams 
flowing southward from the Santa Monica ilountains during Pleisto- 
cene time, depositing much of their load before reaching the ocean. 
Later on wave erosion has cut the plain back toward the mountains, 
materially reducing the di.stance which the streams had to travel 
before reaching the coast and causing them to cut deep trenches into 
the plain. In some of the deep canyons north and northwest of Santa 
Monica, like lower Santa Monica and Temescal. stream terraces are 
well developed, four being recognizable though not with equal e< 
The uppermost terrace stands about 50 feet below the surface of the 
Santa Monica Plain and from 250 to 265 feet above sea level. In Rustic 
Canyon, probably the same terrace, again 50 feet below the level of 
the Santa Monica Plain, is 400 to 425 feet above the ocean. 

About the middle of the magnificent stretch of sea cliffs terminating 
the Santa Monica Mountains along most of their southern side is a 
promontory of basaltic rock called Point Dume (pronounced Dmnc i 
which projects about a mile into the ocean beyond the rest of the 
shoreline. There, protected from erosion by Point Dume. is a small 
stretch of weak Tertiary rocks. Preserved in this area are two marine 
terraces, one about 100 feet and the other about 200 feet above present 
sea level. .\ third terrace level is forming at the base of the cliffs along 
the coast. The elevated terraces indicate two uplifts followed by two 
episodes of quiescence during which the waves indenteil the land ; 
since the last deformation there has been relative stability allowing 
the formation of the present cliffs and terrace. 

This valley is a rudely triangular plain about 20 miles long in an 
east -west direction ; its width at the western end is about 3 miles and 
at the eastern end about 10 miles. The Los Angeles River rises at the 
western end of the plain, flowing to the along its southern side 



(Bull. 158 

and out through hills at the extreme southeast corner. Almost all of 
the valley is a center of active deposition. The eastern half is covered 
by the highly pervious fans made largely of granitic gravel which 
have been deposited by Big and Little Tujunga Rivers and Tacoima 
Creek ; the western half is covered by less pervious cones of smaller 
streams draining from adjacent hills which are composed largely of 
sedimentary rocks. 

Beyond the coast, the Channel Islands, including Anacapa, Santa 
Cruz, Santa Rosa, and San Miguel, extend far enough westward so 
that San Miguel lies due south of Point Conception east of Santa 
Barbara but is separated from it by about 30 miles of ocean. These 
islands evidently were once part of the Santa Monica Mountains, 
westernmost member of the Transverse Ranges, and have been sepa- 
rated by the deformations which have profoundly affected this part 
of the California coast in quite late time. To the southeast are Catalina, 
San Clemente, San Nicolas, and Santa Barbara islands, not part of 
the first group, but all members of the little galaxy collectively called 
the Cliannel Islands. 

San Clemente, typical of the Channel Islands, lies about 50 miles 
south of the Palos Verdes Hills, the nearest point on the mainland. 
The Palos Verdes Hills tliemselves were once an island but have been 
annexed to the mainland by sedimentation. Between Catalina and 
San Clemente is a 25-mile stretch of ocean. San Clemente is about 21 
miles long, 4 miles in maximum width, narrowing to about 1 mile at 
its northwestern end. The greatest elevation, 1,964 feet, lies just a 
little east of the center of the island. Prom the crest, the descent on 
the northern side is very abrupt, dropping in one place 1,800 feet in 
half a mile. The southern slope is more gradual, broken principally 
by a remarkable series of elevated marine terraces. The bold northern 
face is broken here and there by deep gorges. 

San Clemente is a simple tilted fault block not greatly modified by 
erosion, the northern side therefore being a somewhat battered fault 

scarp. The contrast in slope between the northern and southern side is 
coiitiiiiicd below sea level, for 2 miles from the northern shore depths 
(if :i.(i01) feet have been measured, as near Wilson's Cove, wliile at the 
same distam-e I'mni the coast on the opposite side, the water is only 300 
feet deep. 

There are minor faults paralleling the trend of the boundary system, 
and low scarps have been observed along them. 

The outstanding features of the landscape, developed largely on 
the southern side are marine terraces, which are described as out- 
standing for their size, continuity, and distinctness. 

As high as 1,320 feet above sea level, the terraces are so well pre- 
served that they can be traced for miles; more than 20 have been 
recognized. It is evident that the deformation which caused the eleva- 
tion of San Clemente to its present height was interruptetl by times 
of relative quiescence during which the terraces and sea cliffs behind 
them were evolved. 


Baile.v, T. L., Late Pleistocene Coast Ranpe orogenesis in southern California : 
Geol. Soc. America Hull., vol. 54. pp. 15491508, 194:i. 

Davis, W. M.. (Ilaeial epochs of the Santa Monica Mountains, California : Geol. 
Soc. America Bull., vol. 44, pp. 1041-1133, 1933. 

Eekis, Rollin. South eoa.sital basin investigation: geology and water storage of 
valley fill ; California Div. Water Resources Bull. 45, 1934. 

Hoots, H. W., Geology of the eastern part of the Santa Monica Mountains. Los 
Angeles County, California : V. S. Geol. Survey Prof. Paper 165-C, 19.30. 

Miller. W. J., Geomorphology of the southwestern San Gabriel Mountains of 
California : Univ. California Dept. Geol. Sci. Bull., vol. 17. pp. 193 240, 1928. 

Putnam, W. C, Geology of the Ventura region, California : Geol. Soc. America 
Bull., vol. 53, pp. 091-754, 1942. 

Putnam, W. C, and Bailey, T. L.. Geomorphology of the Ventura region, Cali- 
fornia : Geol. Soc. America Bull., vol. .53, pp. 091-754. 1942. 

Reed. R. D., and Ilollister, J. S.. Structural evolution of southern California : 
Am. Assoc. Petroleum Geologists Bull., vol. 20, pp. 1529-1704, 1930. 

Russell. R. J.. Land forms of San Gorgonio Pass, southern California : Univ. 
California Pub. in Geography, vol. 6, pp. 23-121, 1932. 


1 1 III 



Till' sdUtliwesteni corner of California is occupied, except for a belt 
of nuaiiic terraces alou'i the coast, by mountainous land which has 
been called the Peninsular Ran-jes. This <rreat hi^'hlaiul extends from 
the vicinity of Los Aufreles and Kiverside nearly to San Fernando at 
about latitude ;!()° in Lower California, a distance of nearly 300 miles 
with two-thirds of it beinp; south of the Jlexican border. North of the 
ranges lies the Transverse Kaufres Province; at the southern end is 
the desert of San Horja. The average width of the Peninsular system 
is about 50 miles; on the California side of the border it includes the 
Santa Ana Mountains which are detached from the main body. 

The eastern side of the province is strikingly defined, for there a 
great eroded scarp descends abruptly from a more subdued upland 
landscape to the floor of the Imperial-Coachella graben which nowhere 
in the state stands more than a few hundred feet above sea level. With 
few exceptions the highest elevations in the Peninsular Ranges are 
located close to this scarp while the western side slopes much more 
gradually. In California the highest point is Mount San Jacinto 
(10,508 feet), a short distance west of Palm Springs. Santa Rosa 
Mountain farther to the southeast rises 8,046 feet above sea level. 

Viewed as a whole, the Peninsular Ranges arc a gigantic fault block 
which has been raised with tilting upward on the eastern side like the 
Sierra Nevada. Actually, however, this block is divided into minor 
units along subsidiary fractures which either lie parallel to the 
boundary system or at high angles thereto. Each block has had a more 
or less distinct landscape evolution which has depended upon the 
nature and magnitude of movements affecting it. The great eastern 
scarp, simple in places and in others developed by intersecting faults, 
along the front of the San Jacinto and Santa Rosa sections is 
comparable in majesty with that of the Sierra Nevada fronting on 
Owens Valley; it is especially conspicuous west and .south of Palm 
Springs. At this city, the elevation is 445 feet above sea level, while 
San Jacinto Mountain, a little more than 7 miles distant is more than 
10,000 feet higher. For a thousand feet above the CoachcUa Valley, 
this scarp rises abruptly above which there is a considerable reduction 
in slope. This indicates recency of movement elevating a block which 
had advaiu'cd to greater age in the scheme of land.scape evolution, and 
this is further proved by the fact that the scarp is notched by com- 
paratively few deep canyons which have at their mouths only small 
alluvial fans. Although the scarp apparently does not have the actual 
slope of the boundary faidt system, it has not receded very far. South 
of the San Jacinto-Santa Rosa, this boundary declivity, while 
jirominent, is in most places not so high or steep. 

The Peninsular Range resembles the Sierra Nevada also in di.stribu- 
tion of precipitation, most falling over the broad western slope. The 
dominant winds come from the ocean, rise over the highland, and lose 
most of their moisture before reaching its crest. 

Descending the eastern slope, the air is warmed, absorbs moisture 
most of the time, and the climate becomes increasingly arid toward the 
base of the range where it adjoins the desert Imperial-Coachella basin. 
On the western side rain and snow are much less than at equivalent 
elevations over most of the Sierra Nevada. The broad western slope 
of the great Peninsular block together with the distribution of pre- 
cipitation has caused the development of numerous though not very 
large streams flowing toward the Pacific Ocean. Because of the abrupt 
descent of the eastern scarp and the less moisture available, the streams 
are short and small ; they very quickly disappear after reaching the 
mouths of their canyons by evaporation and by sinking of their water 
into the highly pervious alluvial fans. Only the larger floods transport 
debris beyond the margins of the fans onto the flatter floor of the 
desert basin. 

Above the scarp the change in landscape is conspicuous, for much of 
the range shows an advanced topography into which the western slope 
streams have eroded gorges and canyons 500 to more than 1,500 feet 
deep. In places this upland is gently rolling, in others hills or moun- 
tains of irregular pattern rise above its general level, erosion residuals 
which had not been worn away before the great block began to rise 
in recent time. Also particularly near the eastern scarp, there are 
short detached summit ranges, some oriented parallel to the trend of 
the range but most directed more nearly east-west. In California the 
more prominent of these isolated ranges are the San Jacinto west of 
Palm Springs, the Agua Caliente and Cuyamaca farther south ; 
beyond the Mexican border there is the culminating range of San 
Pedro Martir and at the southern extremity of the Peninsular block, 
the Sierra San Juan de Dios. In the western part, this broad seaward 
slope increases from about 1,500 feet in elevation to more than 3,500 
feet as in Cowles, San Miguel, and Otay mountains. It rises to more 
than 4,000 feet in McCains Plateau and over 6,000 feet in the Laguna 
Mountains along the eastern escarpment. The increase in elevation is 
by no means gradual or uniform, for the range has been fractured into 
large and small blocks which have moved more or less independently 
of each other. Many of these blocks stand out as moderately well 
defined plateau areas, while others, less uplifted and usually smaller 
form basins or valleys and valles as they are called. Some of these 
dislocated remnants of a once continuous erosion surface have been 
little affected by the stream invigoration which has accompanied ele- 




I Bull. 158 



' m^m 




'i0 ■ 


Fio. 137. San Jacinto Range near I'alm .Sprinps. California. This part of the ranpe has been elevated by recent moveraeuts ulunR faults auU is broken by a number of 
large active faults within the block. At the mouth of the canyon at the base of the high block is an alluvial deposit brought from the range by flood waters of the stream. The 
eastern margin of the Imperial Valley graben (Coachella section) shows along the lower righthand side. The culmination peak. .Mt. San Jacinto, rises more than 10,000 
feet above sea level ; the floor of the Imperial Valley at Palm Springs is about 400 feet above sea level. Photo by Fairchild Aerial Surrev- 








-3000 -f _-^- 


~_^ ~-r^_I Miocene ~Z^^ ^ — — " IT 

24 ZS 









Fio. 1.18. Top. diaRrammalic section across the south coastal basin, shoving the probable late Pliocene basin of distribution when that part of the area was below 
shallow ocean water. J/(er RoUiK Ecki: Bottom, diagrammatic section along the same line, showing the Pleistocene (Quaternary) basins of deposition when the area was 
mostly above sea level. After Rollin Eckis. 



(Bull. 158 








'""V- -^^-- -^- 

3-rr5>f5-/;'/////|- se« LEVEL 

r-r^XV'V //// -500 
_ <.^>^ — ^^■^>S:^_'>/'////////-iOOO 

b I 2 3 4 S S 7 S 9 10 II 12 13 14 15 16 17 IS 19 

Fig. 139. Diacrammatic section across Ibp Santa Fe and Beverly-Newport uplifts. The Quaternary alluvium is very late Pleistocene, .l/fcr ifo/lin Eckit. 

vation of the Peninsular Range. Examples of these little damaged 
remnants may be seen south of Alpine at 2,000 feet, south and south- 
west of Guatay Mountain at 4.000 feet, and the rather large area of 
the McCains Plateau between Jacumba and La Posta valleys also at 
about 4,000 feet. Below this advanced erosion .surface lies deep residual 
soil and weathered but still coherent rock through which project 
masses of much fresher material. 

The old landscape had been evolved by long erosion prior to eleva- 
tion of the range. It seems to be similar in its topography and may 
once liave been continuous with that in the uplands of tlie San Ber- 
nardino and San Gabriel Mountain:?, and in many remnants scattered 
through the Mojave Desert. This Furface has not been studied in much 
detail hence its history is not well knowni. Whether it exhibits the 
multiple features so tinely showii on the western side of the Sierra 
Nevada has not been determined, but such evidences of recurrent 
uplift and associated dissection are to be expected. 

Ill the Peninsular Range there is a considerable number of basins; 
one of the largest is the Valle San Jose between Palomar, Volcan, and 
Agua Calieiite mountains whose crests rise from 2,500 to 3,500 feet 
above a flattish floor of considerable extent. Others are Viejas, Cotton- 
wood, and Morena valleys. Some of the basin floors exhibit the ancient 
landscape little modified by erosion while others have stood sufficiently 
low relative to their surroundings so that they have received consider- 
able deposits of alluvium or have harbored lakes in which sediment 
accumulated. Field study indicates that these basins actually are 
grabens which either sank as the Peninsular block was being elevated 
or failed to rise as far as their surrouiulings. Thus they are features 
comparable to those found in the Sierra Nevada (Tahoe and Sierra 
basins and various others), to be expected in a great mass which is 
being elevated along major faults. The deformation of such a block 

is complex and it yields to the deforming forces by bending an;l minor 
fracturing, the latter finding more expression in relief features than 
the former. 

At various places in the range there are a number of long, narrow 
depressions which appear to have resulted from erosion in the crushed 
zone of larger faults. 

The recency of uplift of the Peninsular block is testified to by tlie 
boldness and small amount of erosion of the eastern scarp and the 
depth and narrowiiess of canyons cutting both it and the western 
slope. Some have held that the great eastern face is an erosion product, 
though its evolution by this mechanism has not been very clearly 
brought out. However, comparison of its features with those of the 
eastern face of the Sierra Nevada and the clear evidence of a major 
fracture system along the base of the Peninsular block indicate beyond 
much doubt that this scarp is the product of great dislocations which 
have caused elevation of the range and sinking of the adjacent 
Imperial-Coachella graben. The eastern Peninsular scarp is highest 
and most abrupt at the northern end. Farther south in places there is 
a series of parallel northwest trending mountainous ridges, clearly 
fault-block mountains, between which are sharply outlined sunken 
blocks like Collins, Borego, and Clark Lake valleys. The Santa Rosa 
Mountains is the principal of these ridges, with a long, .straight scarp 
a few thousand feet high on the southwest side, above whicli there is 
a slope (tlie old erosion surface) descending to the from 
8,000 to about 6,000 feet above sea level. Beyond is the great ea.stern 
scarp. In other places the eastern front is less simple indicating 
paralle' faulting with distribution of the dislocation along the various 
fractures giving step-fault topograpliy. 

Between the nortlicrnmost part of the San Jacinto section of the 
Peninsular Range and the San Bernardino section of the Transverse 




^ ' .it 


Fig. 140. San Jacinto section of the IVninsular RongeR west of Palm Springs, showing abrupt front which is controlled by recent elevation along faults. Discontinuous 
nlluviiil fans at mouths of canyontj in the range and the relatively flat floor of the Coachella section of the Imperial Valley graben make the foreground. Photo bjf Fairchtld 
Aerial Surreya. 



[Bull. 158 

1 ^ '■ I » * >i !Mj «> MjH lSfc»^K 

Fio. 141. Marine terrace 

and recenUy eroded sea di«E along Palos Verdes HiUs, a one lime isli 

and which bus been joined t„ .he shore, rko,.. Uy F.uchM .Ur.aJ .Sur...,, 




system is San Gorgonio Pass whose crest is about 2,600 feet above 
sea level. Ilifih points on the ranges immediately adjacent rise from 
8,000 to 9,000 feet. Prom its summit, the pass slopes gently eastward 
where it merges imperceptibly with the northern end of the Coachella 
valley. On the western side, the slope is quite as gentle toward the 
Beaumont Plain, but the margin between the pass and this plain, 
while not prominent, is more conspicuous than that on the eastern 
side. The main part of the San Gorgonio depression is a lowland 2 
to 3 miles wide and about 18 miles long; it is a narrow fault trough 
or graben filled to a great depth with sediment of quite recent depo- 
sition. Bedrock comparable with that exposed in the adjacent San 
Jacinto and San Bernardino ranges therefore must stand a consider- 
able distance below the surface of the trough. 

The southern boundary of San Gorgonio Pass is the spectacular, 
battered fault scarp of the San Jacinto Range. At the eastern end "of 
the pass, the sheer mountain front bends from east-west to more 
nearly north-south, and in this angle lies the famous desert resort of 
Palm Springs. The northern margin of the pass is not so conspicuous, 
partly because the high peaks of the San Bernardino Range lie 
farther from its base than those of the San Jacinto Mountains and 
partly because of a foothill belt which lies between the pass and the 
former range. In the narrow fault trough between the two ranges 
there has been greater deposition of sediment from the northern range 
than from the southern, hence the northern side of the pass stands 
300 to 500 feet higher than the southern. 

Although the San Andreas fault passes diagonally along the foot- 
hill belt of the San Bernardino Range, other faults are responsible 
for the difference in elevation between the and the summit of 
the mountains. The Banning fault makes a group of scarps along the 
northern side of San Gorgonio Pass, some of the movements being so 
late that they have tilted recently formed alluvial fans. 

Wind blowing over sedimentary deposits in the pass have swept 
sand into drifts that are found on both windward and leeward sides 
of ridges projecting from the San Jacinto Mountains. Excellent ex- 
amples of sand blasting, the erosive effect of the wind, are found 
near some of the drifts. 

Roughly paralleling the southern California coast and lying about 
20 miles inland are the Santa Ana Mountains which run for some 
distance southeast of the Santa Ana River. The mountains are a fault 
block of rather complex structure which has been elevated on the 
northeastern side along the great Elsinore fault system and tilted 
southwestward toward the ocean. The crest, lying along the northeast 
side of the block, is rather uneven, increases in elevation southeast 
from the Santa Ana River, and culminates in Santiago Peak (eleva- 
tion 5,680 feet). On the northeastern side of the block, the range 
front is a steep, battered fault scarp, drained by short streams that 

run into Temescal Wash at its base. In contrast, to the southwest of 
the crest, long ridges slope toward the ocean. Santiago Creek is the 
principal stream on this side and drains practically all of it. 

The Santa Ana Mountains, like the nearby San Gabriel and San 
Bernardino ranges, have been uplifted during Plei.stocene time. The 
Elsinore fault along which the uplift has occurred is an extremely 
complex system, no single fault running continuously through the 
entire length of the zone. 

The northern side of the range is terminated by the Whittier fault 
which runs westward from the Elsinore zone. Northeast of the Santa 
Ana River, this mountainous belt is continued by the Puente Hills. 
The Puente Hills are relatively low and inconspicuous as compared 
with the Santa Ana block. 

The Palos Verdes Hills are an isolated upland peninsula projecting 
into the ocean along the western side of the south Coastal Plain 
west of the city of Long Beach. The general features of this upland 
resemble those of the islands off the coast of southern California and 
it is evident that during parts of Pleistocene time it. too, was separated 
from the mainland. Northwest of the Palos Verdes Hills a belt of 
irregular sand dunes extends inland from the coast, overlapping the 
lowland and the northwestern border of the hills. 

The peninsula is small, measuring about 9i miles long and 4 to 5 
miles wide; its highest point, San Pedro Hill, stands only 1.480 feet 
above sea level. The crest and most of the upper slopes of the area are 
a rolling upland comprised of smoothly rounded hills and wide, gently 
sloping valleys. Along the lower slopes is a series of marine terraces 
which are being indented by deep canyons that are working inland 
and gradually destroying the rolling upland. The west and south 
coasts of the peninsula terminate in a sea cliff ranging from 50 feet 
high at Long Point to 200 feet at Malaga Cove and 300 feet at Bluff 
Cove. It averages between 100 and 150 feet. Along the east coast at 
the city of San Pedro, the cliff is about 50 feet high. 

The Palos Verdes Hills form a conspicuous uplift along the coast 
where deformation during the late Pliocene, middle Pleistocene, and 
late Pleistocene can be recognized. The boundary between the hills 
and lowland is thought to be a fault, but such does not show at the 
surface. However, this northern boundary has been the most mobile 
section of the entire Palos Verdes area. The strata composing the hills 
have been thro^vn into mostly broad, gentle folds, though in a few- 
places they are steeply dipping and locally overturnetl. 

The rolling upland is believed to be part of an old erosion surface 
developed over a much wider area before the isolation of the Palos 
Verdes Hills as an island. It is characterized by widely flaring valleys 
separated by round crested ridges, the maximum relief preserved 
being about 700 feet. These valleys are sharply contrasted with the 
narrow gorges advancing into the lower slopes from the shoreline. 



[Bull. 158 

When the upland topography was evolved eaiinot be exactly deter- 
mined, but probably it had been eonipleted by early or middle Pleis- 
tocene time. 

A number of undrained depressions are present in the upland area, 
being most numerous at the northwest end. They are thought to have 
been formed by solution of parts of the thin limestone beds that are 
known to underlie the area with consequent settling of overlying 
strata into the voids which were left, though drainage changes also 
may be responsible for some of them. 

Tlie most striking features of the Palos Verdes Hills are the ele- 
vated marine terraces of which 13 have been recognized. The terraces 
range in height above sea level from about 100 to 1,300 feet. The gentle 
slopes on San Pedro Hill above an altitude of 1,425 feet may repre- 
sent a still higher terrace formed wlien the island was completely 
submerged, but this has not yet been proved. The lower and therefore 
younger terraces naturally are best preserved and most easily identi- 
fied ; they are most clearly visible on the windward west coast and the 
southwest coast from San Pedro Ilill to Point Fermin where they 
have been eroded into the most resistant rock. Between the two areas 
the continuity is broken by erosion of the steep slope and by land- 
sliding. On the leeward slopes where waves cut into weak rock, 
terraces are exceptionally wide, but, where the rock is more resistant, 
the weaker wave action developed less well-defined terraces. In places 
the terraces appear to merge, probably because of accumulation of 
non-marine debris after emergence. Locally this non-marine cover is 
at least 100 feet thick. In some places it seems to have spread onto 
still lower terraces concealing the sea cliffs between. The height of sea 
clilTs between the different terraces is not uniform, but actually meas- 
urement is not possible because of later erosion and deposition. 

The terraces indicate that the elevation of the Palos Verdes Hills 
followed the normal pattern, taking place more rapidly during cer- 
tain intervals and then perhaps almost ceasing for a time. The cutting 
of the terraces occurred during the episodes of stability. 

Along the northern border of the Palos Verdes Hills the lowest 
terrace was deformed following emergence and deposition of the non- 
marine cover. Along most of the west coast and almost all the south 
coast, the lowest elevated terrace has been destroyed by erosion de- 
veloping the present terrace at sea level. The valley now occupied by 
GafFey Street in San Pedro was cut across the warped lower terrace 
by an antecedent stream or by a stream which breached the Gaffey 
anticline, running through this section, and captured a stream for- 
merly draining southeastward north of the anticline. It seems prob- 
able that recent slight growth of the Gaffey anticline has caused 
impounding of the water of Bixby slough north of the anticline. 

There are numerous landslides at various places. One extensive 
area forms the hummocky area inland from Portuguese Point and 

Inspiration Point and is explained by movement along a slipping 
plane formed by a water-soaked bed (if tuft'.' A large slump of difl'erent 
type took place in 1929 about a quarter of a mile of Point Fermin. 
A semi-elliptical area extending for 1,000 feet along the sea cliff and 
400 feet inland moved seaward as a body, leaving a main fissure f) to 
10 feet wide in an irregularly fissured zone ')() to 100 feet wide. This 
slide was attributed to sliding on the slippery surface of a shale bed 
inclined seaward in an anticlinal fold. Soon after it was formed the 
main fissure was filled with fossiliferous marine sand from Second 
and Beacon Streets. Movement took place again in 1940 suggesting 
that the slumped mass rotated upward as it moved toward the ocean. 
Exceptionally hea\'y rains in 1941 caused the slide to become active 
again indicating that stability has not yet been reached. 

San Gabriel Valley 

This plain, like the San Fernando, is about 20 miles long, 7 to 10 
miles wide for most of its length, but narrows to little more than 2 
miles at its eastern end. The gentle slope of its surface is to the south. 
Rising abruptly to the north are the high San Gabriel Mountains. 

The debris cone being formed by the San Gabriel River occupies 
the central part of the valley extending from the mouth of the moun- 
tain canyon across the plain and through the Whittier Narrows to the 
Coa.stal Plain. This area of active deposition is extended and west 
of the cone by accumulations of smaller streams coming from the San 
Gabriel Mountains. Dissected older alluvium covers most of the east 
and west parts of the valley and is found elsewhere, and its soil zone is 
reddish-brown, whereas this coloration is not present in areas of active 
deposition. Uplift of the San Gabriel Mountains has been responsible 
for dissection of the cones on that side of the valley where there are 
many high remnants of old cones fringing the mountain front between 
the canyon mouths. The head of San Dimas cone which covers the floor 
of the narrow eastern part of the valley has been cut by streams to a 
depth of 125 feet. Toward the central part of San Gabriel Valley, this 
older dissected surface gradually merges into the surface where depo- 
sition is going on. 

Steep-sided bedrock hills project here and there through the allu- 
vium and contrast strikingly with the general topography of the 
valley. All are near the sides of the valley and around them the alluvial 
deposits are comparatively thin. Wells in the central part of the valley 
show a thickness of 1,000 to at least 2,000 feet for the alluvial fill; 
this can only be accounted for by substantial subsidence of the bed- 
rock, since the deposits extend more than a thousand feet below 
sea level. 

At the east end of the San Gabriel Valley in the vicinity of La Verne, 
the alluvial plain narrows to a width of about 2 miles and then widens 

• Tuft is a volcanic rocl< made of small fragments of lava developed during volcanic 




into tlie iipper Santa Ana Valloy. wliii'li is about 40 miles lonfj from 
west to east. The wicUli of its western part is about 20 miles, and 
tleereases almost to a point at the eastern end. Under tlie compara- 
tively even surface of the valley is an irre^'ular bedrock floor covered 
in places by more than 1,000 feet of alluvium which has come prin- 
cipally from the San Gabriel and San Bernardino mountains. 

The greater part of the upper Santa Ana Valley is covered with 
undissected, recently deposited alluvium, but around the mar^'ins, 
particularly the southern, and at places farther within the basin there 
are eroded remnants of hifiher deposition surfaces with their char- 
acteristic reddish-brown soil zones. 

The Santa Ana River, below the San Jacinto fault at San Ber- 
nardino, has cut throu-rh the older alluvial deposits to depths of 50 
to 100 feet aiul flows on a narrow flood plain which it has formed 
between these hifrh banks. The river lies south of the present area of 
active accumulation of sediment from the San Gabriel Mountains. 
The two facts just presented suprj-'cst that the central part of the 
Santa Ana Valley has been recently .subsidinfr. 

The Coastal Plain extends alon;; the ocean south of the Santa 
Monica Mountains for about 50 miles and extends inland for 12 to 20 
miles. Except for the San Pedro Hills, which are an isolated prroup 
risinjr about 1,500 feet above sea level near the coast line, the plain 
has a relatively even surface broken here and there by low hills and 
mesas. The ea.stern part has been built up from the shallow sea floor 
durin<r relatively late Pleistocene times by deposits Svhich streams 
have broufjlit from the interior, whereas tlie western part is rather 
recently uplifted and only slip^htly modified continental .shelf. Below 
lie thick deposits of Pliocene and Miocene ajre formed when the repion 
stood mostly below sea level. 

It has been shown that oscillations of sea level togrether with defor- 
mation of the earth have at times left certain parts of the plain well 
above the present level of deposition while other sections have been 
submerged below this level. The uplifted areas stand as hills, terraces, 
or mesas which have weathered, usually red or brown soil surfaces 
and are now \niderfroing erosion. In the jiarts which have been sinkiiiL', 
alluvial debris is actively aecumulatinf; and the surface is covered by 
relatively unweathered sandy or silty soil. 

The most conspicuous of these dis.sected areas are two rows of hills 
which have been produced by recent foldinj,' and faultin;; of the plain. 
The first is the Beverly-Newport uplift, a hilly belt extcndinj,' south- 
east from Beverly Hills to Newport Beach and including' the Baldwin 
Hills at Injilewood, Dominsruez Hills, Signal Hill, Landing Hill, 
lluntiufiton Beach, and Costa Mesa. The second row of hills 
begins at Santa Fe Springs south of Whittier where it is scarcely 
visible and ends in the Covote Hills several miles to the east. 

West of the Beverly-Newport uplift, streams have cut into the 
Coa.stal Plain to depths of 25 to 100 feet; between the valleys are 
broad, flat, mesa- or terrace-remnants of a marine surface uplifted in 
late Pleistocene time. This surface extends from the of the hills 
to the coast where it ends abruptly in a series of bluffs. At its northern 
end this marine surface is contemporaneous with the deeply eroded 
surface of alluvial cones alonjr the of the Santa Monica Mountains. 

Between San Pedro Hills and Santa Monica is a .series of old sand 
ridfres which in part at least were offshore bars built up from the ocean 
floor when this section was below sea level. These sand bar ridges 
appear to have provided .sand which has formed dimes covering a 
considerable area south of Inglewood. If this explanation is correct, 
the bars in the Inglewood area have been so modified by the removal 
of sand that their original form is unrecognizable. 

At certain localities on the lower parts of the old marine surface 
referred to above there has been some deposition of products removed 
from higher areas, but in general there has been little covering by 
later sediment since the continental shelf rose above the ocean. 

Streams eroding the western part of the Coastal Plain flow through 
moderately broad alluvial plains covering mature valleys eroded 
below the level of the old marine surface. These plains stand little 
above sea level aiuI the streams empty into sloughs with marshy tide- 
lands. Because the sloughs indicate subsidence, it seems probable that 
the western part of the Coastal Plain stood somewhat higher above sea 
level than it does today, and that the streams now flowing over flood 
plains traveled through broadened gorges now filled with delta and 
delta plain deposits laid down as a rising ocean invaded the mouths of 
the gorges. 

The Beverly-Newport uplift makes an important break in the 
Coastal Plain even though its relief is not considerable. The Pleisto- 
cene sea bottom making the surface of most of the western Coa.stal 
Plain is faulted and folded up over this row of hills and then slope.s 
down on their eastern side where it below very late Pleistocene 
stream deposits. East of the Beverly-Newport barrier, the surface of 
the Coastal Plain is an undis-sected surface underlain by stream 
deposits which extends from the base of the Santa Monica Mountains 
to the vicinity of Irvine. At the two ends this alluvial surface is nar- 
row, but in the middle it is about 15 miles across. 

This unbroken alluvium is the surface of a great trough into which 
three lu-incijial rivers, the Los Angeles, San Gabriel, and Santa Ana 
and various minor streams are pouring debris. Well logs show that the 
stream deposits form a thin veneer below which are at least 1,500 feet 
of marine sediments laid down when the area was below sea level 
during the later part of the Pleistocene epoch. The thinness of the 
stream-laid beds indicates that filling above sea level has occurred in 
very late time. 




I Bull. 158 

The low hills runniug from Santa Fe Springs to Coyote Wash have 
separated a narrow depression, generally known as La Habra Basin, 
lying north of tlie hills from the main Coastal Plain. This basin there- 
fore has been filled with stream sediment as it gradually rose while 
most of the main Coa.stal Plain was below sea level and was receiving 
sediment deposited in the ocean. 

Older stream deposits, folded up over the Santa Fe Springs-Coyote 
uplift, stand above the level of deposition on the central Coastal Plain. 
This older alluvium has been dissected and weathering has developed 
a reddish-brown soil zone in its upper part. 

Elsewhere between the principal rivers, dissected alluvial cones 
with weathered-reddish brown soil zones fringe the north, east, and 
south margins of the Coastal Plain. The surfaces of these di.sseeted 
cones, steeper at their apexes than the present streams, converge with 
them toward the center of the Coastal Plain and finally pass beneath 
the streams. 

Considerably dissected remnants of old marine terraces, which 
include erosion terraces together with beach and inner continental 
shelf deposits, are found along the coast beyond both the northwest 
and southeast ends of the Coastal Plain. Along the southwest side of 
the Palo Verde Hills they are especially wcll-deveioped, seven or eight 
well-defined old shore lines and others less distinct having been recog- 
nized. The highest terraces remnants stands more than 1,000 feet 
above the present shore line, but they are not very distinct because 
of damage which erosion has wrought since their elevation. 

This portion of California extends from the Pacific shoreline to 
the Peninsular Ranges east of the city of San Diego and can be divided 
into two .sections, the coastal mesas which are part of the south Coastal 
Plain and the rugged mountainous section rising abruptly on the 
eastern boundary of the mesas. The two parts are composed of quite 
different rocks and have had quiti' distinct histories. 

The mesa section has a serai-arid climate, the precipitation being 
about 10 inches annually at San Diego and not much greater at the 
base of the mountains. Most of the rainfall comes between October 
and April. The temperatures normally have moderate range, freezing 
being rare in the winter and oppressively hot days equally so in the 
summer. The mountainous section on the other hand receives con- 
siderably more rain and snow in the higher parts during the winter. 
Summer days in some of the valleys have temperatures reaching 100°F. 
and more. The higher peaks and ridges cause speedy condensation of 
the eastward drifting air currents as they rise along them, giving 
precipitation of more than 40 inches a year on the western slopes of 
such ranges as the Palomar and Cuyamacas. Within the mountains 
precipitation decreases somewhat in most places but exceeds 20 inches 

The mesa section extends for many miles north and south of the 
San Diego region ; on the north it is continuous with the south Coastal 
Plain of the Los Angeles Basin while on the south it passes beyond 
the Mexican border. The mesas either extend to the where they 
are cut off by cliffs being eroded along the jiresent coast or descend 
by a series of terraces which are separated by bays or a coastal plain 
from the shoreline. In width the mesa section ranges from 6 to 14 miles 
and in height from sea level to more than 800 feet. The most con- 
spicuous mesa which is nearly fiat-topped and only slightly dissected 
stands at elevations ranging from 300 to ")50 feet. 

The coast line within this area has two promontories, a broad north- 
ern one formed by the mass of Solcdad Mo\intain near La Jolla and a 
southern at the isolated, north trending Point Loma. There are two 
embayments, a smaller one, Mission Bay or False Bay as it was for- 
merly called, between Soledad Mountain and Point Loma, and the 
larger and deeper San Diego Bay which is protected by Point Loma 
and a long sand spit called the Silver Strand, Coronado and North 

The eastern boundary of the mesa .section is determined by the 
abutment of Tertiary sediments against much older rocks forming 
the foothills of the mountains to the east, though this boundary is 
rather indefinite in places where the Tertiary sediments thin out to 
a veneer of soil upon the older formations. 

The mesas are terraces cut by wave action and covered by a thin 
veneer of rather coarse marine deposits; there are several of these 
terraces, the higher being much dissected and less easily identified. 
The principal terrace is called the San Diego, below which arc others 
developed on the western margin of this mesa. The lower terraces arc 
of comparatively small area, but are quite distinct wliorc tlioy have 
not been destroyed by later erosion. 

The San Diego Mesa has been trenched by streams from the moun- 
tains into a number of sections to which various local names are 
applied. The name Otay is used south of Otay Valley and Linda Vista 
Mesa or Terrace north of the San Diego River. Southward the mesa was 
elevated higher and more rapidly than to the north, for near the 
Mexican border, its surface stands about 550 feet above sea level while 
just .south of the San Diego River, the elevation is little more than 
300 feet. 

The surface of the San Diego Mesa appears to be an almost feature- 
less plain broken here and there by rather deep gorges cut by streams 
flowing from mountains to the west. Actually, however, there are 
many gentle undulations, such as long, low ridges which may have 
been beach ridges. Some doubtless have devclopetl because of differ- 
ences in weathering and erosion in various parts of tiie mesa. Also 
there are many small hillocks 3 feet or more high and having a basal 




Kiu. 142. Elevainl nurine terrace at Torrey Pines. A new terrace and sea cliff are being developed bj waves alone the present shore line. Photo bn Fairchild Arrial Surreift. 



T,., .«. .. ,..,. -.. .. '■'Ss;i!^zixa::S^:s:='SX::iX^^^!r^^^- """ "-'" "" """ '" 




San Dieco Harbor (Yacht Club Sortion) showing Inns ho4>kptl saml bar stiindinE snmf distance off shore. Peninsular Ranjres 

in backf:riiund. Photo by Spenre Air Photot. 



[Bull. ir)S 

diameter of 10 to 20 feet, calletl prairie mounds. It is thouplit that 
these small eminenees may represent both tlie accumulation of sand 
about and the irrej;ular removal of sand between bushes or otlu'r clumps 
of ve{;etation. .Since the hillocks are present not only over the top of 
the mesa but alonfj its marjrinal slope, the probability is that they were 
formed as the land rose and the ocean cut terraces below the San Diejro 
level. Duriiifr such an epoch, there probably was plenty of available 
sand which the wind drifted inland and piled wherever an obstacle 
was present. 

The beach ridges previously referred to are numerous north of the 
San Diego River where they have caused the partial develoi)ment of 
a trellis drainage by the streams eroding Tecolote Canyon and smaller 
canyons east of La Jolla. Elsewhere in the mesa section the drainage 
is the normal dendritic or treelike type. The beach ridges are composed 
largely of sand which either shows poor stratification or none at all. 

The San Diego Mesa is but little damaged by stream erosion and 
therefore is in the youthful stage. The northern portion, especially the 
section immediately adjacent to the .south rim of Mesa Valley and 
Linda Vista terrace to the north is less dissected than the part to the 
south, probably because of the harder rock in the Linda Vista area 
and the closer spacing of valleys south of Choyas Valley. 

Many of the canyons cutting the mesa have quite steep slopes and 
their tops meet the mesa surface in a sharp angle. 

The San Diego Mesa probably is also represented by parts of the 
upper surface of Point Loma though faulting in that area has tilted 
some of the remnants, and also by a much less evident surface about 
half-way up the southern and western slopes of Soledad Mountain 
where again tilting has occurred. 

The western sides of the San Diego Mesa and the sides of some of 
the larger valleys exhibit well-preserved remnants of lower, younger 
terraces, of which there are four principal levels and others much 
less well developed. The principal ones are the Avondale, standing 
200 to 250 feet above sea level ; the Chula Vista (100 to 130 feet) ; the 
Nestor (25 to 100 feet) ; the Tia Juana (20 to 50 feet). Southward 
from Otay Valley these terraces, like the San Diego Mesa, stand at 
progressively higher elevations and are separated by greater vertical 
distances. Since the terraces represent surfaces of marine erosion 
covered by a thin veneer of deposits, it is evident that uplift has been 
greater and more rapid toward the Mexican border than farther north. 
All of the terraces are probably younger than middle Pleistocene ; they 
testify to dominant vertical elevation in the San Diego region while 
farther north there was considerable compressional deformation dur- 
ing the same epoch. 

In the older rocks of the Peninsular Range east of the coastal mesa 
belt, remnants of a much older surface can be distinguished clearly 

which has been called the Poway Terrace because of its conspicuous 
development in the hilltops south of Poway Valley. East of Linda 
Vista Mesa it can be seen at the tops of hills 800 to 900 feet above sea 
level at the west but slo|)iiig u|>ward to elevations of 1,100 to 2,100 
feet 5 to 20 miles eastward. The terrace was not developed by wave 
action, as were those previously described, but represents a surface 
evolved principally by rivers which had reached advanced maturity 
or possibly old age. Many eminences rose above the general level, but 
it is uncertain which of these were developed by erosioTi and which by 

The same surface is preserved in parts of the vipper drainage basin 
of the San Diego River as a rolling upland only partly destroyed by 
canyons evolved during a late cycle of uplift. Also in parts of the 
region aromid Potrero and extending with interruptions far to the 
east of Carpo and for an unknown distance into Lower California, 
there is an ancient erosion surface which may well be the equivalent 
of that just described. 

Some have considered this elevated surface as an ancient, nuich 
dissected and warped marine terrace evolved during the Eocene epoch, 
but it seems much more probable that it was a surface developed above 
.sea level primarily by rivers not earlier than Pliocene time. 

Differences in geologic structure aiul rock resistance have caused 
various irregularities in the shoreline of the San Diego region. Resist- 
ant masses of rock form promontories because waves cannot so easily 
destroy them as they can weaker materials. The embayments or coves 
between the headlands have been partially filled by streams emptying 
into them and by sand driven in bj' waves. North of La Jolla, the San 
Diego Mesa has been quite evenly attacked by wave erosion with the 
formation of a long .stretch of cliffs at the of which there is a 
narrow beach. The land appears to be sinking slowly so that during 
storms the waves are able to attack the base of the cliffs, undercutting 
them with resultant landslides. In this section the rate of cliff retreat 
is fairly rapid. 

About a mile south of Scripps Institute near La Jolla, where there 
is a mass of resistant rock, the coast projects about a mile into the 
ocean. Because of differences in resistance of various parts of the rock 
to erosion, waves have sculptured caves, .small arches, and irregular 
stacks. A few feet above high tide is a narrow bench or terrace which 
some have believed to represent recent uplift; on the other hand it 
may be the product of erosion during especially severe storms. South 
of La Jolla the coast is irregular for about 3 miles to the beginning of 
Pacific Beach, where weaker rocks and other factors have made easier 
wave erosion. In this section is a terrace upon which the community 
of Pacific Beach is located. Debris evolved in erosion of this terrace 
and also that brought in by streams has been shifted southward by 




waves and coastwise currents to be deposited almost completely across 
the mouth of Mission Bay wliich was formerly known as False Bay 
and by the Spanish as Puerto Falso. A long spit with a narrow tidal 
opening at the south is called Mission Beach. 

Mission Bay appears to be a structural depression, which may be 
the southern downwarped part of Soledad Mountain. Mission Bay is 
very sliallow and is being gradually filled by the encroaching delta 
plain of the San Diego River. Intermittent streams from various 
canyons also are adding to this deposit. 

A broad point, known as Bay or Crown Point, is an extension of 
La Jolla Terrace projecting into Mission Bay from Pacific Beach. 
Its surface is largely covered with windblown sand. When the sea 
cut the Crown Point section of La Jolla Terrace, it must have swept 
up the low ground between Mission Bay and San Diego Bay isolating 
Point Loma as an island. 

The low flat land between Old Town and the northeast margin of 
Point Loma is part of the delta plain of the San Diego Kiver. As the 
delta plain has growni, the river and its tributaries have occupied 
many different positions in traversing it, as is shown by earlier maps 
of the area. Like most streams in this region, the San Diego River has 
infrequent floods, but when they come a large amount of sediment is 
brought down to be added to the delta plain and the submarine delta 
section to the seaward. Some shoals and small islands have been formed 
in Mission Bay by tidal currents and waves. 

Point Loma is a long promontory extending from the tidal flats of 
Mission Bay for 6 miles southward, where it landlocks the western 
portion of San Diego Bay. This peninsula is about 3 miles wide at the 
north, narrows to a little more than a mile and a half at the south and 
stands about 300 feet above sea level. Its flattish top is possibly the 
equivalent of the San Diego Mesa, from which it may have been 
isolated by subsidence of the land round about in late Pleistocene time. 
Parts of the eastern and western side of Point Loma have a narrow 
terrace standing 2.) or more feet above sea level. The western shoreline 
is quite irregular owing to variations in resistance of the rocks. 

San Diego Bay is a long, roughly crescentic, landlocked arm of 
the ocean with which it is connected by a narrow channel on the 
side of Point Loma. The south and southwestern shore of the bay con- 
sists of North and South islands and a sand spit connecting them and 
attaching both to the mainland. The two islands may be remnants of 
the Nestor Terrace (elevation in this part of the San Diego region 
about 25 feet), but their connection with the mainland resulted from 
the construction of a long crescentic sand spit by the northward drift- 
ing of debris brought to the sea by the Tia Juana River which enters 
the ocean near the Mexican border. Spanish Bight is a small, shallow 
re-entrant of San Diego Bav between North Island and Coronado. 

San Diego Bay is relatively shallow except where dredging has 
maintained a navigable channel. Tidal scour at the entrance has been 
aided by the building of a jetty which may eventually have important 
effect upon wave and current action along Coronado and South Island. 
Shortly after it was built, violent storm waves eroded a large part of 
Ocean Boulevard west of Hotel del Coronado. A small stone jetty or 
breakwater was constructed .southeast of the hotel in 1897 and 189S 
to protect it from wave erosion, and a sea-wall of quarrj' stone was 
built westward along Ocean Boulevard in 1906 and 1907, and was 
repaired in 1911 and 1912 because of heavy damage by storm waves. 

The mainland shore of San Diego Bay is mainly salt marshes and 
tidal flats except where the Nestor terrace produces a small bluff just 
above high tide line. Intermittent streams from Las Choyas, Sweet- 
water, and Otay Valleys have constructed small, marshy delta plains. 

There is no delta at the mouth of Tia Juana River which flows into 
the ocean south of San Diego Bay near the Mexican border because 
waves and currents sweeping along the shore remove debris about as 
fast is it was deposited. 

The Nestor Terrace is continuous from the foot of San Diego 
Mesa — or Otay Mesa as it is calle<l on some maps — westward to the 
beach north of the mouth of Tia Juana River, except for a little swale 
extending from Tia Juana Vallc.v northwestward to the southern end 
of San Diego Bay. This drainage depression crosses the highway just 
west of Nestor and Palm City, and appears to represent erosion by 
overflow of former great floods which swept down Tia Juana Valley. 

Most of the valleys crossing the mesa have flattish floors above which 
rock walls rise very abruptly for 300 or more feet; they have been 
eroded into relatively weak sediment by streams rising in the moun- 
tains to the east. Only Otay Valley has a rounded bottom and may be 
younger than the rest. The flat floors have been evolved by the filling 
of gorges with alluvium that extends below present sea level. It is 
probable that during the lowered oceans of the glacial stages, the 
streams cut their valleys through the weak material to meet the falling 
shoreline. Then, as the sea has risen, the valleys have been gradually 
filled in by sediment. Measurements indicate that some of the alluvial 
fills which started as deltas and rose above sea level as delta plains 
extend at least 120 feet below the present surface of the ocean. 

In the mountains east of the mesas, the streams flow in deep, narrow, 
young canyons evidently eroded as these ranges have risen to their 
present height in the very late part of earth history. In fact, the 
mountainous mass is still being elevated. 

Faulting has broken up the mountainous mass so that actually it is 
a series of blocks which have been elevated to various extents, though 
there is a general increase in height from the foothills on the west to 
the high crest peaks on the east ; this increase in elevation however. 

ff.,;sJ"iK'=s£;;:s;;nr,=i:w::;irs;;-:=;'=;r:J™:ts;,;i'i^^ ~- - '-■'»' ■ "- 




is far from uniform. The Palomar Mountains, Volcan Mountain, the 
Lacuna Mountains, and various other units appear to be fault blocks. 
In the western part of the Peninsular Ranges the trend of the prin- 
cipal faults appears to be roughly northeast-southwest corresponding 
to the trend in other parts of this highland. Rolling uplands already 
described are present in various parts of the mountains, but whether 
they are parts of a single erosion surface or of various erosion sur- 
faces has yet to be determined. 

In a region where deformation has produced such profound changes 
in the landscape during late geological time, movements are still going 
on in various sections, perhaps in all parts. Topographic features 
produced by movements along faults have already been described and 
many of these show along the active faults of the state. WTiat is not 
so generally known is that certain areas are slowly rising or sinking. 
Evidence of this has been described along the sea coast, but we are 
inclined to associate this with the past and not think of it as going 
on today. In the Los Angeles section, instrumental surveys have shown 
that certain parts either are being elevated or are being depressed so 
rapidly that surveys made a few years or even a few months apart 
show vertical movement has gone on. As a basis for the surveys, mean 
sea level, whose position is determined by some federal agency such 
as the U. S. Coast and Geodetic Sur\-ey or the U. S. Geological Sun-ey, 
is used. A brief summary of some of these unstable areas follows to 
give the reader a picture of the reality of deformation which probably 
goes on everywhere at all times though in most places at rates too slow 
to be determined. 

One of the sinking areas includes a large part of the Beverly Hills 
and some adjacent territory to the east and south, perhaps 15 square 
miles in all. The maximum rate of subsidence centers approximately 
at the intersection of Melrose Avenue and La Cienega Boulevard 
where it amounts to about one five-hundredths of a foot per year, at 
least from 1925 to 1937. While this is unusually high, the effect would 
not be noticeable in a good many years. Surveys made in 1929 and 
repeate<l in 1937 showed that part of Venice and of Playa del Rcy 
also had sunk ninety-six hundreds of a foot in the 12 years, with the 
maximum at the intersection of Forty-second Avenue and Trolley- 
way in the southern part of Venice. 

In contrast, west of Inglewood there is a rising area in which the 
detected movement has been about three hundredths of a foot a year. 
This appears to be actual elevation and not merely relative to 
denees taking place east and west. This rising area is adjacent to a 
fault zone which extends from the south base of the Santa Monica 
Mountains near Beverlj- Hills southeast beyond Inglewood as far 
as Signal Hill north of Long Beach. As horizontal movement 
takes place along the fault, which apparently runs through strong 
rocks at some depths, the sedimentary beds overlying the fault bend 

into small anticlines which are arranged en echelon. Eight oil fields are 
located on or close to this deformation zone — Beverly, Inglewood. 
Potrero. Rosecrans. Dominguez, Long Beach, Seal Beach, and Hunt- 
ington Beach. Small hills such as Dominguez Hill and Signal Hill 
appear to be anticlines formed along this fracture zone which is called 
the Newport-Signal Hill uplift. The fault apparently is active for 
epicenters of several recent earthquakes are located along it. 

From Inglewood eastward for several miles there is another sub- 
siding area. 

In the Los Angeles and Long Beach Harbor areas changes of level 
noticed by engineers appear to be upward and downward in periods 
of about 7 months. At Long Beach and the country round about 
evidence of rather rapid elevation and depression has been deter- 
mined in the last 20 years. The low. marshy, lagoonal section between 
the Palos Verdes Hills and the low. rounded, but rather conspicuous 
hills along the Newport-Inglewood uplift appears to be subsiding. 
Stream, marsh, and beach deposits here are rather thick, indicating 
relative subsidence for much longer time than human historv- in the 
area probably includes. Before being interfered with by man. the 
Los Angeles River deposited enough sediment in this coastal area to 
offset the effect of sinking; otherwise there doubtless would have been 
a large emba^inent in the Los Angeles and Long Beach harbor areas. 
Along the eastern margin of this low area are the hills of the Newport- 
Inglewood uplift, the conspicuous being Signal Hill near Long 
Beach. hills are anticlines developed by deformation of sedi- 
mentary layers which overlie the fracture zone. Both Signal and 
Dominguez Hills have been proved to rise intermittently ; earthquakes 
occurring along the Newport-Inglewood fault may control this upward 
movement. Between earthquakes when the crust is more stable, the 
hills seem to subside as does the area between them and the Palos 
Verdes Hills. 

In Long Beach itself both elevation and subsidence have been deter- 
mined, most of the movement being downward. Elevation occurred 
between 1930 and 1932. before the highly destructive earthquake 
centering along the Newport-Inglewood fault zone in 1933. and again 
between surveys made in 1940 and 1941. There was a moderate earth- 
quake in 1941 and others later, but what effect these had on the 
movements is not known. Such scanty evidence as is now available 
suggests that uplift occurs prior to disturbance along the Newport- 
Inglewood zone, but this may be coincidental. Instruments which have 
been set up in the area may show definite relations when enough 
recordings have been made. 

For the Long Beach area in general there appears to be elevation 
in the northern part and subsidence toward the southwest with an 
intermediate zone where no change of level has been recorded. Thus 
the area is being warped with tilting downward to the southwest. 



[Hull. l,j.s 

Kill. 1411. I )('ransi(li'. Culifoniiii. 'I'he city is hiiill tm a bniail tPrrace. .Miiuntain.s in the liac kcround arc |iait iif Ilii" Santa Ana KanjiP. Pliolu hi/ Fnirrhilil Arii:il Morrj/*. 




Signal Hill has an independent subsidence area which includes the 
summit of this anticlinal dome. Between 1926 and 1931 it subsidctl 
nearly half a foot. Oil-field operations may be responsible for the 
sinkin;: here and at Venice and Playa del Rev. 

In 1941 the concrete foundations of a number of oil wells situated 
on Terminal Island in the Long Beach Harbor area showed evidence 
of subsidence at an extraordinarily rapid rate. The sinking apparently 
was local though in an area of slower depression. The shortening of a 
shallow superficial layer of sediment and high pumping rate from 
deep water-wells operated by the U. S. Na\-j' in the prior month 
probably were contributing causes. 

The of the elevation and depression are varied. Earth move- 
ments play a very important part and probably are responsible for 
most. Also the drying out and compaction of clay layers and other 
natural volume decreases in sedimentary rocks are a factor. In addi- 
tion the works of man play a part — extraction of water, oil. and gas; 
drainage and deflection of water either already below the surface or 
that which would sink in were the artificial controls not used. 

Such changes afiFeet the surveying of the land for they may prevent 
establishment of much needed stations which do not change in eleva- 

tion. In addition certain ones may damage drainage canals, sewers, 
drawbridges, and other structures and they have bearing on the 
behavior of oil in producing fields. Insignificant though the move- 
ments may appear to be and taking place very slowly in most cases, 
over long periods of time they can produce profound alterations in 
the earth's relief such as have been described. 


Dudley. P. It., (leology of a portion of the Perris block, southern California: 
California Div. Mines Kept. 31. pp. 487-.')06. 19.1i>. 

Eckis, Rollin, South coastal basin invpstigation — geolopy and ^ound water 
capacity of valley fill : California Div. Water Resources Bull. 45, 1934. 

Ellis, A. J., and I^e. C. H.. <_fe<»logy and cround waters of the western part of 
San Diego County, California : U. S. Geol. Survey Water-Supply Paper 446, 1919. 

Hertlein. Ij. G., and Grant. I'. S. HI, Geology and paleontology of the marine 
l*liiK-ene "f San Diego, California : San Diego Soc. Xat. Uist.. vol. 2. 1944. 

Miller, W. J., Geomorphology of the southern Peninsular Range of California : 
Geol. Soc. America Bull., vol. 46. pp. LlrW-lSea. 1930. 

Russell, R. J-. I^and forms of San Gorgonio Pa-ss, southern California : I'niv. 
California Pub. in Geography, vol. 6. pp. 23121. 1932. 

Sauer, Carl, Land forms in the Peninsular Range of California as developed 
about Warner's Hot Springs and Mesa (trande : Univ. California Pub. iu Geog- 
raphy, Vol. 3. pp. 199-290, 1929. 



Knowleiljie of the contour of the ocean floor has been grreatly 
increased in recent time because of the development of instruments 
with which rapid determinations of depth can be made. Formerly 
depths had to be measured by weighted lines let down to the bottom, 
a time consuming process particularly in the deeper waters. Measure- 
ments obtained in this way were fairly numerous in places where 
navigation made them necessary but were widely scattered elsewhere, 
consequently our concept of submarine landscape was extremely 
sketchy. In the last two or three decades instruments called fathometers 
have been perfected which measure depth by reflection of sound waves 
from the sea bottom, a much more rapid method. In many places, 
especially in the shallow waters, the topography has been quite 
accurately worked out and good maps have been made of the suboceanic 
floor. In deeper waters, although depth measurements are still too few, 
they are numerous enough so that our concept of the relief has been 
materially revised. 

Materials from the ocean floor are obtained by dredging and coring, 
but of course these operations can extend only to very shallow depths. 
A moderately complete knowledge of surface materials on the ocean 
floor has been obtained at shallow depths and even from the deep 
ocean, but nothing is kno\vii of what lies below. Most of the floor of 
the ocean is covered with sediment and the lower layers undoubtedly 
have been consolidated into rock. In a few places in shallow waters 
there are indications of the thickness of deposits but nothing is known 
for the deeper. 

Practically everywhere around continental and island coasts there 
is the flattish continental shelf sloping gently out to sea from the shore 
line as much as a few tens to a few hundreds of miles. Beyond this is 
the continintal slope which descends somewhat more or much more 
abruptly to the great depths of the ocean. However, off the southern 
California coast, the picture is quite unique for there is a series of 
ranges and basins extending for about 160 miles that is much more 
closely related in structure and topography to the land than to the 
deep ocean. The continental shelf is very narrow; beyond it is the zone 
of irregular topography termed the continental borderland. The nor- 
mal landscape of the shelf is quite different from that of the land as 
the contours are much simpler ; farther out in the ocean the basins 
extend deeper below their surroundings than basins on the land and 
the tops of mountains called submarine banks are much flatter. 

Because of the basins in the continental borderland off the of 
southern California, withdrawal of the sea from this area would leave 
a_group of large lakes, some up to 1,000 square miles in area, and 
comparable with many of those now existing within the continent. 

In depth these imaginary water bodies could exceed any in the United 
States, the Santa Cruz Basin being 2,880 feet below its rim and the 
St. Nicholas basin 2,370 feet. Crater Lake in Oregon, deepest in North 
America is about 2,000 feet while the deepest spot in Lake Tahoe in 
the Sierra Nevada is more than 1,600 feet below the surface. On the 
other hand, there are basins not containing lakes deeper than any 
mentioned ; for example. Saline Valley, which lies between Owens 
Lake and Death Valley, has its lowest outlet 3,900 feet above it.s base. 
The area of the submarine basins off the coast of southern California 
is about 6,300 miles, approximately a fourth of the total extent of 
the continental borderland in that .section. The basins are roughly 
elliptical and are elongated northwest and southeast. Submarine find- 
ings indicate that their walls are long, steep slopes broken by a few val- 
leys, though there are abrupt changes in the direction of the walls 






catalina is. 






I i,oeo 






Fio. 147. Sections across the basins and trouRhs off the coast of 
southern Cnlifornia. Depths by U. S. Coast and Geodetic Survey and 
the E. \V. Soripps Institute of Oceanography, After F. P. Shepard and 
K. O. Emery. 




[Bull. 158 

Basins off the soutbprn California coast which would hold lakes if the 
sea were withdrawn. After F. P. Shrpard und K. O. Kiitery. 

apparently controlled by folds or faults. Soundings taken across the 
basins indicate relatively flat floors broken by moderate irregularities. 

The rims of the basins which would represent outlets of the lakes 
if the sea were withdrawn become deeper below sea level toward the 
.southeast, and most of the basin floors deepen in the same direction. 
Such islands as are present rise from the northern part of the shelf. 
All of this suggests that there may have been downwarping in a 
southeasterly direction, a submergence which would account for the 
notable widening between the upper margin of the continental slope 
and the shore line which so sharply contrasts this region with the rest 
of the California borderland. 

The relief of this borderland is diverse. At least one peak, probably 
conical in shape, is present southwest of the Coronados Islands and a 
few of the banks are elliptical in plan. Most of the eminences are long, 
relatively narrow ridges, small portions of some of them rising above 
sea level to form the islands off the southern California coast. The 
higher parts of the borderland are comparable in size to the short 
mountain ranges of the adjacent lands. The San Bernardino Ranges 

rise about 9,000 feet above adjacent basins, while the submarine San 
Juan Seamount stands roughly 10,000 feet above neighboring Hats. 
Santa Cruz Island has an elevation of about 9,000 feet above the floor 
of the Santa Cruz submarine basin, while Cafalina Island comjiares 
with the Santa Ana Mountains, each about G.OOO feet above surroinid- 
ing territory. 

In contrast with the highly sculptured contours of the mountains 
above sea level, the submarine slopes even where steep in general are 
relatively smooth. However, there are exceptions, as for example the 
man.v small canyons in the bank on which San Nicolas Island is 
located, distinct valleys around" Cortes and Tanner Banks, and one 
off Catalina Island. Even on the land, some mountains are much more 
intricately dissected than others. 

Conspicuous features of this submarine region are the flattish tops 
characteristic of the submarine banks, features yet unex|)lained. 

The sea floor in this southern California section compares with the 
adjacent land in showing more than one direction of trend of ridges, 
the prevailing being northwest-southeast, like those of the Santa Ana 
and San Jacinto moinitains on the land. On the north, an 
trend cuts across the other, probably a continuation of structures of 
the east-west Santa Ynez, Santa Monica, San Gabriel, and San Ber- 
nardino Ranges. Below sea level there is also a north-.south trend, 
showni in a ridge southeast of San Clemente Island. This island to- 
gether with Catalina and the Palos Verdes Hills on the land line up 
in a north-south direction. A few oval submerged areas are northeast- 
southwest and thus are at right angles to the dominant trend. 

Many of the steep slopes in this borderland area in all probability 
arc fault scarps, as for example otf San Clemente, Catalina. and Coro- 
nados Islands and ott'shore from the Palos Verdes Hills which now are 
attached to the land but formerly were one of the islands. 

The basin between Santa Catalina and San Clemente islands appar- 
ently is bounded by fault scarps and if so is a graben. There are certain 
complexities in the scarp on the San Clemente side which have not 
been explained. 

In many places the trends of the submarine fault scarps are broken 
by offsets in fashion quite similar to that observed in .scarps of like 
origin on the land. 

Under the ocean marring the normal smoothness of the continental 
shelf and frequently extending far down the continental slope are 
deep, narrow gorges very closely simulating those eroded by rivers. 
That many of them are branching further increases the likeness. Some 
are confined largely to the continental slope into which they break to 
depths of many thousands of feet while others project back into the 
shelf, virtually to the shore line. Some are located olTshore from the 
mouths of rivers running on the land while others do not have this 




• S END 









Vui. 1-10. Profilps at various latitudes alon? the California coast showinj: liolh surface anil suhmarinc features. Section .\ is in two parts. 
Depths from l'. S. Coast an«l (JeoHetie Surve.v. After F. P. Shepnrd and K. O. Kmery. 


I Hull. 158 


Air PhoioM 

Fig. 150. 

A small sea slack at Morro Bay aloni; the San Luis Obispo oc.ast. Stack hiis h.'cn Ii.'il I., liin.l h.v a san.l liar fonu.-il I,, « in 
which shuts iilf the hay except for u iiarnnv channel near the island. I'holo by Spencer Air Photos. 

Cti'MI. IW} "liil 1-1. 

1- ;i l.i.j Lar 







2000 3000 



KiG. 151. Cross sections across the beadward portion of 
Monterey submarine canyon. Depths from sounding.«i by I*. S. 
Coast and Geodetic Survey. After F. P. Shepard and K. O. 

relation. The origin of these so-called submarine canyons has been 
much debated but as yet no satisfactory explanation has been 

In the southern section of the continental borderland, most of the 
submarine canyons found along the coast do not extend to verj- great 
depths. JIany are found where the scarps are offset or where the trend 
of an escarpment changes, but some are located in different settings. 

From Point Conception to Cape San Martin, the submarine land- 
scape is strikingly contrasted with that farther south. Except for one 
extensive valley and the gap which it forms in the continental slope, 
this section is relatively featureless. 

Between Cape San JIartin and Point Ano Xuevo north of Monterey 
Bay. there is the greatest concentration of submarine canyons along 
the California coast and the canyons are the largest. Furthermore the 
gently sloping continental shelf and the long rather straight escarp- 
ment of the continental slope so prominent farther south are missing. 
The slope is much broken, not particularly steep, and is cut by many 
of the canyons. 

In this section there are short canyons extending not far out beyond 
the shore line, while others are much deeper and break the continental 
slope, the hugest of the lot being Monterey Canyon, which may even 
extend beyond the margin of the continental slope into the floor of 
the deep ocean. The inner portion of this giant gorge can be compared 
with the Grand Canyon of the Colorado River in Arizona but the outer 
part is a broad trough with gently sloping walls. The gorge section Ls 
50 miles long, the trough about 56 more. 

South of Point Sur a fault extends to the coast and its seaward 
projection follows a submarine scarp which diverges southeastward 
from the coast. The group of submarine canyons in this section ter- 
minates headward along this structural line and two of the canyon 
heads appear to be deflected so that they parallel the supposed fault. 
This straight portion of the coast with mountains rising boldly above 
the shore line and a very narrow continental shelf possesses all charac- 
teristics essential to a fault coast. 

Monterey submarine canyon and its tributaries also reflect struc- 
tural features observed along the adjacent coast. Carmel Canyon, a 
large tributary coming in from the south, parallels the coast, and 
either is cut along a fault or in relatively weak rock between adjacent 
resistant materials. Beyond the deep part of Monterey Canyon, the 
broad trough previously mentioned extends seaward for about 22 
miles. North of Monterey Bay the submarine canyons also terminate 
in a similar trough. The origin of these broad troughs is not known. 

Beyond the slope off the southern part of this section a submarine 
mountain named Davidson Seamount, 16 miles long, 7 miles wide, and 
rising 7,000 feet above its 2-mile deep ocean base, is comparable with 



[Bull. 158 





Kic. 152. Cross sections alonR Diidtlle nnd outer parts of Monterey submarine 
canyon. Sections ./. 7i' and /* show the troucb-like character of the outermost part 
of the canyon. Depths hy l*. S. Coast and (Jeodetic Survey and Scripps Institute of 
Oceanography. After F. P. t^hepard and K. O. Emery. 

San Juan Seamoiint in the southern section first described. It lias tlii-cr 
or more peaks and two or three apparent depressions in it.s siininiit, 
which are about "jOO feet deep and are believed to be craters. Davidson 
Seamoiint like its counterpart farther south is probably a volcano. 

Northward between Point Ano Nuevo and Shelter Cove, the sub- 
marine canyons start well out to sea and are largely confined to the 
continental slope. This section includes the San Francisco area where 
the shallow continental shelf extends outward for 25 miles, the great- 
est distance along the entire west coast of the United States, though 
considerable' less than off the east and south coasts. 

The great marginal scarp descending to the deep ocean is less sharply 
defined for there is a series of slope changes such as are found in the 
section immediately to the south. In the outer slope there are many 
canyons some of which may extend as deep as 12,000 feet. Southwest 



Fio. 153. Map showinp relation betweeti land rivers and submarine canyon 
axes off the coast in the Monterey Bay area and along the front of the Santa Lucia 
Mountains. After F. P. Shepard and K. O. Emery. 




of the Farallon Islands, two mountains, which have been called Guide 
and Pioneer seamounts rise about 3,000 feet above their surroundings 
at the base of the continental slope. Possibly they are volcanoes. 

Between Shelter Cove and the Eel River, the chief feature is a 
prominent submarine escarpment, called the Gorda or San Andreas, 
which extends for about 70 miles from Point Gorda. This zone also is 
notable for its large submarine canyons some of which extend almost 
to the coast. 

The Gorda submarine scarp runs almost due west and except in one 
place is comparatively straight. Its height varies from zero at the edge 
of the narrow continental shelf to about 6,000 feet 30 miles out to sea. 
Beyond this point, the height decreases to about 4,000 feet at a distance 
of 60 miles from where it starts. Possibly the scarp continues farther 
out to sea though the indication is strong that it dies out within the 
next 20 miles. Along most of its length this imposing declivity is topped 
by a narrow ridge which has a series of summits rising to within 1,200 
feet of the ocean surface, but beyond these hills the ridge broadens and 
is covered by water reaching 4,800 feet in depth. Along the north base 
of the ridge, there is a long, narrow depression or series of depressions. 

The structure along the Gorda escarpment appears to be far from 
simple, but evidence now available is insuflScient to give a very com- 
plete picture. The escarpment is unique not only for California, but 
for the world, since no place is known where there is a similar declivity 
running normal to the general trend of a coast. Epicenters of earth- 
quakes have been located in the general vicinity of the scarp suggesting 
possibly that it is still forming. 

The San Andreas fault has been traced as far as Point Arena, but 
beyond that there is difference of opinion regarding it. Some say it 
goes out to sea, while others believe that there is a return to the coast 
at Shelter Cove and an extension inland beyond that point. The evi- 
dence for the extension as far as Shelter Cove came from the develop- 
ment of a rift at that locality at the time of the 1906 earthquake. One 
authority holds that there are two faults beyond this point, one ex- 
tending north-northwest to the coast at the mouth of Humboldt Creek 
and the other paralleling it about 2,000 feet inland. The rift noted 
above still is plain and can be traced across Point Delgada to the coast 
on the northwest, and from there about half way between Points 
Delgada and Gorda. About half way between these two coast prom- 
inences there is another riftlike feature. Toward Point Gorda the 
broken zone is less conspicuous but the formations are much con- 
torted. The presence of a fault along the coast also is indicated by the 
way the structural features are cut off at the coast rather than being 
traceable in the topography of the adjacent sea bottom. Also Delgada 
submarine canyon beads against a steep ungullied mountain side 
while most others are located off land valleys or lowlands, suggesting 
a shift in the position of this canyon by horizontal movement such as 

has been characteristic of the San Andreas fault. At the head of Del- 
gada Canyon is a straight escarpment sloping at 45 degrees which 
also suggests faulting. All of this evidence indicates that the San 
Andreas rift extends along the coast almost as far as Point Gorda 
and if so, it should extend out to sea nearby. The great Gorda sub- 
marine escarptment previously described therefore may be the sea- 
ward prolongation of the San Andreas fault. 

The zone off Cape Mendocino is broken by submarine canyons some 
of which are very large. One to the south can be traced seaward for 
more than 40 miles and to depths of more than 9,000 feet, while others 
have been followed 2,000 and 3,000 feet below sea level. North of the 
Gorda scarp, the canyons are related to land valleys, as for example 
the large ones in the area off the mouths of the Eel and Mattole Rivers. 

From Eureka beyond the Oregon boundary, there are few sub- 
marine canyons or other spectacular topographic features. 

It is noteworthy that on either side of the three most pronounced 
breaks along the California coast Point Conception, Monterey Penin- 
sula, and Cape Mendocino are the largest submarine canyons. To a 
lesser degree the short canyons of the southern California coast can 
be related to projecting points of land, but in no case, either with 
major or minor projections, are the canyons located directly off the 
points. Submarine canyons are particularly rare in the steepest escarp- 
ments especially where the escarpments are topped by ridges, and they 
are almost as rare in the gently sloping portions of the continental 
shelf and the smaller banks. 

If the principal tributaries are included, the number of known sub- 
marine canyons along the California coast is about 66, of which 18, 
including most of the larger ones, head within half a mile of the shore 
line. The other 48 start between half a mile and 30 miles from the coast 
with most between 3 and 5 miles. The gradients or slopes of the canyon 
floors are rather high, comparing with those of land canyons cut into 
mountain ranges or fault scarps, and there does not seem to be any 
serious interruption in this steepness at least to depths of 6,000 feet. 
The cross sections of the gorges are V-shaped in all but the deeper 
portions where some apparently widen into or are tributary to flattish 

Dredging and coring operations have been carried on in 21 of the 
California submarine canyons and rock has been discovered in the 
walls of 17 of these; in only one, Newport Canyon, has this work been 
carried on sufficiently to make reasonably certain that solid rock is 
not present. Most of the rock obtained is soft Tertiary material some 
of it little more compacted than recent sediment, but in some places 
limestone, compact sandstone, and conglomerate have been found. 
Near the head of Dume Canyon of Dume Point in the Santa Monica 
region basalt was obtained from the head of the canyon which cor- 
responded with basalt exposed on the point above sea level. Santa 



[Bull. 158 n; 

s I 


Aerial phot<^raph of South Farallon Island. Marin CouDty shore line in distance ; June 1940. Sea Lion or Saddle Rock is in the fon^round. The rock of the 

Farallon Islands is granite. Photo courtesy V. iS*. Coaat Guard. 



[Bull. 158 


Fir. ].-.«. Aerial phntocraph of Snuth p-iirnllon Islaiul. Midille Farnllon in the distance; .Iiine 1(149. Pholo courlriu V. S. Coatt (liiard. 




Monica Canyon may be out in pranite thoutrh the evidence is not posi- 
tive. Carmel Canyon is quite certainly cut in granite and a steep wall 
along Monterey Canyon showed the same rock to a depth of 3,900 feet. 
In three places resistant rock was met on one side of the canyon while 
the other was composed of unconsolidated sediment. 

Submarine canyons in sea floors where large quantities of sediment 
are being deposited must mean either that the canyons have been very 
recently depressed below sea level or some process operates below sea 
level to keep them open. 

The explanation of these remarkable submarine gorges has been 
actively debated. Some hold that they are river canyons which have 
been submerged below sea level either by the notable sinking of sec- 
tions of the land or eroded during much greater sinking of sea level 
in the Pleistocene glacial stages than most authorities admit. Others 
believe that they have been formed by some type of crustal deformation, 
by the work of submarine currents or submarine springs, by land- 
sliding, or by the occasional disturbances of the ocean when violent 
undersea earthquakes occur. No single process so far suggested ex- 
plains the excavation of these gashes in the ocean floor, and this is to 
be expected for few geological features are simply evolved. Whether 
the complete answer to the question of the origin of the submarine 
canyon will ever be obtained is a matter of considerable doubt because 
of the difliculties of undersea exploration and the fact that direct 
observations are impossible. 

The greatest scarp along the California coast is the continental 
slope which separates the deep ocean basin from the continental shelf 
in the northern area and from the continental borderland in the 
southern section. This escarpment is continuous along practically the 
entire California coast and may also extend off that of Lower Cali- 
fornia. It is offset in certain places. Near Point Conception the scarp 
is set shoreward but after about 30 miles it returns to the general 
position. In other places the north side is set shoreward apparently 
by dislocations along cross faults but without return to the general 
position a.s at Point Conception. However, in spite of the offsets, the 
continental slope comes back in line with the same gently curving 
trend which shows off southern California. 

The structural trends offshore are not only shown by fault scarps 
but also by submarine ridges. The general north-northwest trend char- 
acteristic of the coastal ranges of California is well shown in various 
parts of the sea floor, while the east-west cross trends in the Los 
Angeles-Santa Barbara region also are expressed by east-west trends 
in the adjacent sea bottom. 

Farallon Islands 

Lying about 30 miles offshore from the Golden Gate are the small 
F'arallon Islands which are clearly visible from the hills round about 
San Francisco Bay on a clear day. The group includes seven islets: 
the largest, South Farallon and a few nearby rocks; Middle Farallon, 
about two and a half miles north of South Farallon; and North Far- 
allon, which are five rocks about 5 miles still farther northwest. Beyond 
North Farallon are Noonday Rock which is almost awash and C'ordell 
Hank submerged under 20 fath<ims (120 feet) of water. All of 
units form what is called by some the Farallon Ridge running parallel 
to the shore line from the vicinity of the Golden Gate to Point Reyes. 

On South Farallon is an important lighthouse originally established 
probably between 18.52 and 185.5. During the early part of the last 
century great numbers of fur seals and otters were caught on and 
around the islands and immense quantities of bird eggs were gathered 
and sold on the mainland. The latter activity was ended in 1909 when 
the islands were made a bird refuge now under the jurisdiction of 
the U. S. Coast Guard. 

The Farallons are composed of granitic rock which is deeply weath- 
ered at the surface. The rock is broken by many joints and probably 
by faults whose most conspicuous trend is northwest-southeast. Many 
channels have been worn by wave attack along these fractures. A little 
west of the center of South Farallon. two of these channels meet from 
opposite sides at high tide dividing the island into eastern and western 
parts; this gorge is called the Jordan River. The amount of rock re- 
moved by wave attack in these channels testifies to the power of the 
waves as they sweep in and out, abrading the rock with the sediment 
which they transport and knocking out joint blocks as the waves dasli 
against the rocks. 

Wave-cut terraces are conspicuous on the South Farallon. .standing 
about 50 feet above sea level. The buildings of the Coast Guard are 
located on one and another is at the west end of the island. Where 
the terraces join the higher parts of the island at the base of original 
cliffs eroded by the waves, there are elevated sea caves and surge 
channels like those along the present shore. 

Nothing is known as to the nature of Middle and North Farallon. 


Tjawson. A. C, The continental shelf off the coast of California, Natiooal Re- 
search Council, Bull., vol. a pp. 3-23, 1924. 

Shepard, F. P.. and Emor.v. K. C, Submarine topoprnph.v off the California 
coast, Geol. Soc. America, Spec, paper 31, IMI. On pp. 161-166 of this moaograpli 
is an extended list of articles dealing with the subject. 

Hunna. (i. D., Geolo^j' uf the Farallon Islands : California Div. Mines Bull. 154, 
p. 301-310. 1951. 



San Jose-Mount Hamilton District* 

The top(if.'rii|)liy of imu'li iif the Coast Ranges is vigorously youth- 
ful, that is. the oaiiyoiis are deep and rather narrow and there is little 
or no flat land along their bottoms. The streams are cutting down- 
ward. In some parts, however, the landscape has reached late youth 
or early maturity with the streams widening the lower parts of their 
valleys which have flattish surfaced alluvial fills. The canyons also 
have widened out considerably. Thus erosion and deposition may be 
going on along the same drainage system. In the San Jose-Mount 
Hamilton district, the more advanced phase is met, though the develop- 
ment is far from uniform throughout the area. 

The cutting of canyons and their headward growth is the principal 
feature of the present erosion cycle, but there is clear evidence in 
various places of an earlier phase of canyon erosion which is indicated 
by in slopes along the canyon walls. 

From evidence which has been recently gathered, it appears that the 
mountains of the district have been elevated twice in rather recent 
geological time. The older of the two surfaces mentioned above seems 
to have been a canyon complex though the valleys were shallower and 
wider than those now being developed. Their bottoms stand about 
1,000 feet above the bottoms of the new gorges. Standing still higher, 
up to L.'iOO feet above the floors of the late canyons, is an older surface 
which appears to have been a gently rolling late mature or perhaps 
old landscape which is represented by extensive areas into which the 
canyons are cutting. 

Healdsburg District t 

A report published after this manuscript was written gives a brief 
account of landscape evolution in the Healdsburg district of the north- 
ern Coast Ranges. 

It has long been recognized that the ridge crests of this region and 
farther north into the Klamath Mountains stand at roughly similar 
elevations above sea level, though the elevations change from one 
locality to another. Such ridge crests are said to be accordant. It has 
been believed that they represent residuals of an ancient surface which 
was elevated during the rise of the Coast Ranges during Pleistocene 
time. Between Healdsburg and the coast, the dissected surface of the 
Mendocino Plateau or Mountains is between 1,900 and 2,200 feet 
above sea level ; in other places it stands higher or lower even passing 

• Crittenden. M. D.. Jr.. Geology of the San Jose-Mount Hamilton area, California : 

California DIv. Mines Bull. 157, pp. 11-14, 1951. 
t Gealey. W. K.. Geolon' of the Healdsburg quadrangle, California : California Dlv. 

Mines Bull. 161, pp. 41-45, 1950. 

below sea level. Whether the ridge crests actually represent the eleva- 
tion of an old land.scape is doubtful, for there may have been a general 
lowering of the divides between canyons as erosion proceeded. Cer- 
tainly there are no flat-topped areas remaining which may be inter- 
preted as residuals of the surface. Since the present landscape is a 
succession of ridges and canyons giving a mountainous rather than 
a plateau topography, it is quite probable that the ridge crests stand 
somewhat below the surface from which they have been cut, even 
though the ridges have maintained general accordance of crest level. 

The surface of the Mendocino Plateau or Mountains was consid- 
erably warped by the deformation which elevated the Coast Ranges 
during middle Pleistocene time, hence it stands at distinctly ditferent 
elevations in various parts of the region. Warping of ancient land- 
scapes is a common feature of their deformation. The old, eroded 
landscape also is present in the Mayacmas Mountains which lie north- 
east of Alexander Valley. 

The ancient landscape referred to above appears to have been devel- 
oped by late Pliocene time. While in general it was a surface of quite 
low relief, there were gently sloping hills which rose above broad 
valleys. There is a series of well developed river and marine terraces 
in the area which indicate that the uplift was spasmodic as always is 
the case. Some of the later terraces certainly were developed after 
the principal deformation closed. 

Russian River. The Russian River is the largest drainage line in 
the Healdsburg area and one of the most important in the northern 
Coast Ranges. Its course through the ranges is striking and its his- 
tory is complicated because of the series of events which has occurred 
since the river started to flow. The lower Russian River cuts across the 
Mendocino Mountains in a deep, narrow canyon ; in this section the 
river appears to be antecedent, that is the drainage existed before the 
mountains rose and was able to maintain its course across them because 
the rate of uplift was matched by the rate of erosion of the cross canyon. 
The long .section of the river stretching northward from the Llano de 
Santa Rosa probably is subsequent for it follows a zone of faulting 
which parallels the trend of the ranges. 

Before the uplift of the Mendocino Mountains, the Russian River 
was a consequent stream which developed on the Mendocino block and 
flowed oceanward because the regional slope was in that direction. 
Other consequent drainage roughly paralleling the Russian River is present. An example is the Navarro River which flows into the 

(231 ) 



[Bull. 158 

I'acifii' Ocean f mm the crest of the Meiulocino Range about 20 miles 
northwest of Healdsburfr. The Navarro River is in direct line with 
a long valley trending southeast from the crest to join the Russian 
River. Tlie latter segment also is in line with Big Sulphur Creek which 
Hows into the Russian River from the southeast. At Yorliville there 
is a u'imhjap between the valleys of Navarro and Big Sulphur Creeks 
indicating that the Navarro was beheaded by the extension of the 
Russian River in its subsequent section. A windgap is a short, aban- 
lioned gorge through which a stream formerly flowed. 

Along the subsequent portion of the Russian River, wide valley 
sections are interspersed with narrow. In the Ilealdsburg district at 
least, it is evident that abnormal widths of the valley are controlled 
by the presence of weak strata in the deformed belt. 

The curious passage of the Ru.ssian River through Sonoma Rock 
south of Jimtown appears to have re.sulted from superposition, the 

stream having been let down by erosion (lirongh a younger landscape 
into one more ancient. 

The winding path of the Russian River fliro\igh 'he canyim between 
Alexander Valley and Healdsburg again is the result of tlie structural 
control of its course. Also the prominent curves in the river between 
Wilson ({rove and Guerneville probably arc controlled by structure. 

The last erosion level which carries across wide valleys and far up 
tributaries is correlated with late submergence which drowned nuiny 
valleys along the coast and created San Francl.sco Bay. This sub- 
mergence may have been caused by subsidence, but more probably was 
the result of the rise of ocean level as the great ice sheets of the last 
glacial stage diminished in size or disappeared. More recently there 
seems to have been slight uplift or sinking of ocean level for the river 
has cut from 20 to 2.5 feet into its deposits. This may he as.sociated with 
some increase in volume of ice stored on the earth since the end of the 
Climatic Optimum. 


Abon Ijike. SO 
Adobr Valley. "II 
Aftoii Basin. Sl>. HI 
Aifua i'niienlr. 107. 200 

Springs. 107 
Alaliiuna Hills. (H. I") 
.Mnine«lii I'reek. 17-. 170 
Alani.. River. 10.3. KM. IftS 
Alaska. l.">. 27 
.\lralr;il Islanil. 170 
Aliler Creek Caiiyon, 121 
Aiex.m.ler Valle.v. 2:» 
Alkali I.:ike. SI 
All--\meriran Canal, 107 
Alnmiinr. ."» 
Alpine. 20i> 

County. 14 
Alluras lll.ll:t 

Connty. 80, 81 
Aniboy. .sn 
Anieriean. 15. If* 

liasin. no. 147 

Canvon. 2.% 

Kiver. 4:i. r.-2. W 147 

.Vini>s. no 

Anacapa. l.*^> 
.\ncel Islanil. 170 
Anlart-rii-. 27 
Anticline l{i<l;;e. 1.'2 
Arlinekle. 147 
.\rsiis Mountain. 74 
Kanp\ 71. 7."t 
.\ri»nni. 107. 22:: 
.\rr.iv.iSe<-.i. !>4 
AshfonlMill. 7:t 
Avawiitz Mountains. SO 
Avenal tiap. I. "2 
Avontlale. 2U> 
Awahnee Il.ilel. :!l) 

Itailwater. 72 
Itasilail. .'<!) 
Makers tiel.l. 22 
Hal.l IVak. 17i; 
Kalilwin Hills. 20.'> 
Kallnrat. 74 
Kail Mountain. 11!> 
Italloon IVinie. :!0 
Hanner Canyon. 107 

i'eak. ." 
Ranninc. !>!► 

fault. 2ai 
Rarnarrl. 4(1 
Barstow. !>1 
Basin. Ranees province. 0. l.'j, 10. 27. (B. 04. 70. SO. 

Bencn Sliwt. 204 

Bear Butte. 127. 12s 

Creek Canyon, ISli 
foot Cave. 113 
paw Cave, 11.3 
River. 147 
Beaumont Plain. 20.3 
Benton-BtMlie. 70 

Station. 76 
Berkeley Country Club, 176 

Hills. 164. 170, 172, 176 
Berryessa Valley. 104 
Beverly Hills. 20,-.. 213 
Newport, 205 
Bighorn Plateau. 30 
Bigpine. IfS. M. 66. 6S. 69 
Creek. 30 
Sulphur Creek. 230 
Tujunga River. KM 
Bullyehoop Mountains. 141 
Birch Mountain. 19 
Bishop. 1.3. t« 

Creek. Kt. 57 
Bixbv slough. 2fM 
Black Butte. 122. 127 
Mountains. 72 
Range. (H. 71,72 
Blue Ijike. Xi\. 177 
Bluff Cove. LtM 
Blythe. '.M 
Riiling Lake. 131 
Holani. 120. 127 

Creek. 12.S 
Bnlinns Bay. 170 

I.ngmm. 166 
Borax Lake. 170. ISO 
Borego, no. 2tm 

Valley. 107 
Boy Scout Hill. 132 
British Columbia, 1.5 
Brokeoff voUiino, 131. 132 
Brown Mountain. 74 
Buckingham Peak. 177, ISO 
Buena Vista, 1,52 

basin. 150 
Reservoir. 150 
Bullion Motintains, 80 
Bumpass Mountain, 132 
Huribnri Ridge. 164 
Burney Mountain, lift, 1,30, 1.^5 
Burnt ljiva.S2. Ill 
Butte County. 147 
Creek. 121 
Vollev, 110,120 

Cache Creek. 146. 177. 170. ISO 

Canyon. 177 
Caibour Mountain, 13ft 
Cajon Pass. 185. 187 

Calaveras Reservoir, 55 

Caldera, 80 

Caldwell Cave, 115 

California, 113. 185, 189, 206, 219, 220, 225, 229 

Coast, 27, 170, 172, 180, 194, 197, 219, 

Ranges. 13, 139. 141, 152, 157. 177, 
Development Company, 103 
Callahan, 111 
Camp Curry, 30 
Canada, 10 

Canada del Diablo, 186 
Canadian border, 119 
Canby, 111 
Cantua Creek. 150 
Cape Mendocino. 225 
San Martin. 223 
Captain Jack. 113 
Cargo Muchacho Mountains. 99 
Carmel Canyon, 223. 229 
Carpinteria plain. 1S7 
CaiTio, 210 
Carquinez Canyon, 172 

Strait. 14. 145, 172 
Carson Range. 18. 21 

Valley, 18 
Carriio, 99 

Creek, 99, 107 
Gorge, 107 
Ca.scnde Gulch, 128 

I-akes. 41. 4.3. .V. 

Mountains. 122. 128. 1.30. 139. 145, 146 
Range, 9, 111, 119, 120, 121, 129, 1.39, 145 
volcanoes. 122 
Cascadia, 15, 145. 157 
Castle Crags, 142 
Catalina. KM 

Island. 220 
Cathedral Rocks, 38 
Spires, 40 
Cedarville, 80. Ki. 85 
Cenoioic, 10, 152, 157 
deiwsits, 7.3 
era. 17. 181 
Tertiary. 18 
time. 16 

Tolcanics. 139, 141. 145 
Central Plateau. 131 

Valley Project. 55. 1.39, 142 
Chagoopa Plateau, .50 
Chalk Mountain. 180 
Chalone Creek, ISO. 181 

Valley. ISO 
Channel Islands. KM 
Chaos Crags. 132. 1.34 

Jumbles. 132, 1.34. 1.^5 
Chester. 130 
Chic.1. 146 

Creek. 147 
China Mountains, 139 

I 233 I 


Cliiquito Crepk, 14 

rho(t>Inte MinintJiins. 107 

Chovas Vallf.v. '.'lO 

Chiiln Vistii.21(l 

CiiKler Cone. 127. 1S2. 1S4. 13."j 

Cirquo Ppjik. 4i> 

siiiniiiit. 47 
rinromont. is;) 

Crii-k. 17r. 
riiirk Uikci;(i<i 
Clark.^burK. 147 
Clear I-nke. 8<i. 111. 113. 1G4, 177. 170 

hasin, 177 
Climalii- Optimum. 2M. 232 
Cna( hfllii viUli-.v. !K). imi. 1(W. 2(a 
Ci>a]iui;n, l.'>2 
Coast UaiiBC belt. 141, l."i<) 

Uimces. n. 22, 47. 141. 14.".. 140. I.". ItiO. 1&4, 
170, 2») 
Coast Hills, IK.-. 

I'laiii, 203, 204. 20.'), 200 
Cocopa Mtmntains. lO.S 
Cold Creek. 177 
Collins, 2(H) 

\alle.v, 107 
Colorado, 1(«, KM, lOrt 
Aiiuediut, 04 
riesert.O, N!t, 00 
Uivcr. !I0. 103. 107. 108.223 
Valley. 04 
Colimiliiii plateau. 03, 111 
Coliis,T t^ounty. 147 
Condrey Mountain. 130 
Cop<'o r)ant. 121 
Lake. 121 
Cordell Bank. 220 
Cordoiiiees Creek. 170 
Cnn.nado. 200. 21 1 
Coronados Islands. 220 
Cortes. 220 
Coso Mountains. 00 

Rnnjie. 71 
Costa Mesa. 20.^> 
Cosumnes Hiver. 147. I'^O 
Cottonwood. 200 

Pass. 4r. 
Uance. 107 
Coyote Canyon. 107 

Creek. IIU. 1S.-1 
Hills. 20.- 
Wash, 2(«i 
Cowles, 107 
Cracked Craps. 43 
Crater Lake. 210 

Basin. 132 
Mountain.04, OS. on, 119 
Crescent City. 130. 141 
Crater. 132 


Cretaceous. 10. 17. 141 

period, 22. 145, 157 

seas, 2.^ 

time. 63, 157 
Crowu Point, 211 
Crystal Cave, ll,-> 

Springs. 164 
Cucnmouga fault, 189 
Cuyamaca. 197 
CuyaniHcns, 200 


DaKcett, 89 
Dalton Canyon. ISO 
Darwin. 47 

Hills. 71 
Wash. 71 
I>avi<ls<tn Seamount,223 
Death Valley. 0. 27. 63. 64. 71, 72. 73, 74. 75 

Scntty's Castle, 73 
r)eer Mountain. 120 
Delcada Canyon. 225 
Desert Center. 107 
Desolation area. 4,3 
basin. 4.3 
IjHke. .')3 
Valley, 41, 43 
Devil's Basin, 43, 53 

(;olf Course. 73 
Kitchen, 131 
Postpile. 60 
Punchbowl. 80 
Diablo Range. 164. 172 

.section. 147 
Dinkey Creek. 29 
Divisii>n Creek. 69 
Dumineuez. 21.3 

Hills. 205 
Donner I>ake. 5.3. 55 29 
Dos Palmas, 107 
Double Head, 111 
Drakesbad, 131 
Duck Flat, S3 
Dnme Canyon, 229 

Point, 229 
Dunsmuir, 142 
Dwinnel Resen-oir, 121 

Eagle I^ke. 86 

Peak, 31, 132 
range, 107 
Rock. 119 

Mountain. 119 
Kagleville. 85 

Lake, 85 
East Peak, 104 

Echo Lakes hasin, 4,3 ' 

glacier, 43 
valleys, 43 
Edgewood, 141 
Eel River, 225 

El Capitan, 31, 32, 38 

I'errito Hill, 172 
Elk Valley. 100. 172 
El I*asu Mountains, 80 

Portal. 31. 32 

Prado. 152 
Elsinore fault. 203 
Emerald Bay. 41, 43 
Eocene, 10, IK, 185 

epoch, 22, 23, 210 
Etna, 142 
Eureka. 141.142. 225 

Full Creek Mountain. .'>2 
Fallen Leaf. 41 

l>ake, 55 
Fall River, 113 
Fandango Valley, 80 
FalseBay, 206. 211 
Farallon Islands. 172. 229, 225 
Feather River, 15, .52. 145 
Fish Creek. 57 

Lake Valley, 69 

Mountain, 107 

Springs, 103 

School, 69 
Fort Bidwell, ,S5 
Friant Dam. -"m 
Frink Spring. 103 
Fryxell. Fritiof. 19 
Funeral Ranges, 64, 71 
Furnace Creek, 72 

Inn, 72, 73 

riabilnn Mountains. I.SO 
(laffey anticline. 204 

Street. 204 
Garlock fault. 7.5. 89 
(Jarner Mountains, 129 

Peak. 130 
riarnet I^ike, ,52 
Genoa Peak, 21 
Geysers, 1.31 
Gibson Peak, 1.39 
Gila River. 04 
Valley. 'M 
Gilbert. G. K..63 
Gilta. 141 

Glacial epoch, 18, 25, 26, 27, 29. .30, 57 
Glacier Peak. 122 
Point, 31 
Glen Alpine, 43 
Glendale, 18!» 
Glenn County. 146 
Godel Creek. ,57 
Golden Gate, 27. 164. 170, 172, 229 

Canyon, 172 

International Exposition, 170 

Strait, 172 
Gold Lake, .52 
Goler Well, 89 



Goosp Lake. 63. 145 

Vallex, 82 
(.iiHJseiu'sl. 119 

volcano, 120 
Gorda. 225 
Graben. 19 
Granada Ranch, 121 
Grand Canyon. 223 
Granite Oreek, 14 
Grant I-ake. 78, 79 
Grapevine Canyon. 107 

Ranges. 64, 71 
Grass Lake, 43 
Gray Butte. 122. 128 
Great Basin. 89 
Plains. 13 
Viillev. 9. 13. 14. 22, 25. 47. 142. 145, 150, 152, 

157. 170, 172 
Western Divide, 45. 51 
Greenlnnd. 27 
Grilzly Peak. 129. 130. 176 
ItroundhoR Cone. 57 
Guatay Mountains. 200 
Guerneville. 230 

Gulf of Ivower California, 99, 103, 108 
Gull Lake. 78. 79 
Guyot Flat. 49 

Haicht Mountain. 129, 130 
Half Dome, 30. 31.40 
Moon Lake. 43 
Valley, 43 
Hall Canyon. 1.S7 
Harkness volcano. 131 
Hat Creek. 131. 134. 135, 136 
Hays Canyon Range, 82. 85, 111 
Hayward. 176 

fault. 170, 176 
rift, 176 
system, 176 
Healdsbunt. 2.30 
Heather Lake. 43 
Hemet Valley. 107 
Hetch Helchy Reservoir. 55 

Valley. 40 
High Rooky Uke, 83 

Valley. 179 
Hitchc<H-k summit, 47 
Hockett Peak, 30 
Hollister. 180 
Hollywood. 193 
floney Jjikr. 18.86 
Hoopa ^'aIley. 142 
Hoover Dam. 94. 106 
Horubrook. 141 
Horn Canyim. 185 
Horse Cnmp. 12.8. 120 
IVnk. 129. 130 
Hursethief Butte. 120 
Ranch. 120 
Holluni. 127 

glacier, 128 

Hotel del Coronado, 211 
Howard Peak. 177 
Humboldt Creek. 225 
Humphrey Basin. 53 
Hungry Hollow Hills. 147 
Huntington Beach. 213 
Mesa, 205 
Hyampon, 142 

Idaho. 82, 111 
Igneous rocks, 17 
Ikes Peak, 119 
Illilouette Creek. 52 
Imperial-Coachella. 197. 200 

trough. 99. 106 
Valley, 94. 99. 103, 1(M, 107, 108 
Inconstance Creek. 128 
Indeitendence. 19. 68 

Uke, 53 
Indian Butte. Ill 
wars. 113 
Wells. 100 

Valley, 75 
Indio. 100 

Hills. 99. 107 
Inglewood. 205. 213 
Inspiration Point. 204 
Inyo Mountains. 57. 69 
Range. 69 
-White Mountains, 64 

Jackson, 55 
Jack's Peak. 43 
Jacumba, 200 
Jess Lake, 86 

Valley. 83, 86 
Jimtown. 230 
Johannesburg. 89 
June Ijike. 76. 78, 79 
Jurassic. 10. 15. 16, 17 

fold-faulting, 23 
Mountains, 157 
period, 15, 17, 157 
strata, 130, 141, 142. 145 
time, 57 

Kane Spring, 100. 103 
Kaweah Basin. 30. 51 
group. 4.'» 
River. 15. 52 
Kegg. 120 
Kelseyville. 177 
Kennedy Canyon. 185 
Kern, 57 

basin. 51 

Canyon, 25 

Lake. 55 

River. 14. 15. 22. 29, 45. 49. 150 

Canyon. 22. 30, 45, 46, 47. 50. 51. 55 
Kettleman Hills, 1.52 
Plain. 152 

King Canyon. 25 

City, 180 
King's Basin. 51 

Creek Valley. 131 
River. 15. 29. 45. 52, 145, 150 
area. 30 
Kingston Ranges, 89 
Klamath. 139 

area. 141 

Falls. 111. 113 

Mountains, 9, 16, 55, 128. 139, 142. 145. 

157. 230 
region. 139, 141, 142 
River, 121, 139. 141 
Valley. 120 
Klinker Mountain. 75 
Koip. 47 
Kouoctj. 177 
Konwakitaon. 127 
Kuua, 47 

La Cima. 152 

Cienega Boulevard, 213 
Laguna Dam. 04 

Mountains. 107. 213 
La Habra Basin. 206 

Jolla.206. 210. 211 
Lake Annia. 83 

Cahuila. 103. 107 

City. 85 

County. 177 


Merced. 166 

Russell, 76. 80 

Tahoe. 9. 13. 14. 18, 21, 29, 41, 43, 55, 63 

Pyramid Peak, 13 
Yosemite, 32 
Landing Hill. 205 
I^ngley, 13, 46 
La Posta valley. 200 
Ijis Choyas, 211 
Lassen County. 80. Ill 
Dome. 134 
Park. 127 
Peak. 132. IM. 135 

Volcanic National Park. 130. 131. 136. 181 
I^st Chance Mountain. tM 
Laurel Canyon. 193 

I-ava Beds National Monument. Ill, 113, 129 
La Verne. 204 
Leach Point Mountains. 89 
Le Conte Divide. 45 
Leevining. 78 

Canyon, 76 
Iab«rty Cap, 30 

Gap, 172 
I.4ebre Mountains, 89 

Linda Vista Mesa, 206, 210 
Lintpuasb, 113 
Lion Mountains, 186 


I.iltle Deor Mountiiin, 120 

liliiss Muuntiiin, 11S>, VU) 
Kern ctliiyoiis, 57 
Merced fHiiyuii, ;10 
Red Cones, r»7 
Sbnst.l Vulley. 120 
TiijunKH liiver, IIM 
Wbitney ('reek, Ij7 

Meadow, 57 
Yosemite canyon, lis, 55 
Valley, 32. 40 
Livermore, 170 

Valley, 164 
Lingo Creek, 104 
Llano de .Santa Uosa, 230 
Lone Pine. 13, 47. IKl. 07 

Peak. 1.3. 49 
Long Beach, 1S5. 203, 213 

Harbor. 213, 215 
Point. 204 
Valley. 82, 83, 185 
Loon I^ke, .52 

Los Angeles, 9, 16, 76. 185, 189, 197, 200, 213 
aqueduct, 63 
basin, 193 
region, 94 
River, 193 

-Santa Barbara region, 229 
GntoB Creek, 145, 150 
Lost Hills, 1.52 

Creek, 131, 132, 134 
Lake, 86 
River. 113 
Lover's I^ap, 43 
Lower Califuriiia, l.~> 

Klamath Lake. Ill, 113 
I^ke, 85 

Madeline Plains, 80 
Magee Mountain, 135 
Malaga Cove, 204 
Mammoth crest, 52 

Mountain, 62, 57 
Pass. 57 
Manitoba, 10 
Manix. 91 
Manly Lake. 73 
Manzanita Lake. VH) 
Marble. 139 

Fork, ■Ml 
Maria Mountain rungCH. 94, 107 
Marin Blork, l*i6 

County, 170, 176 
peninsula, 1((4, 160, 170 
Marysville. 145. 148 

basin. 147 
Mason \'alley. 107 
Mattbes. Dr. F. E.. 13. 19 
Matlole River. 225 
Mayacnias Mountains. 230 
Me«n Hills. 99. 107 
Medicine Lake Highland, 111. 113. 128. 129. 130 


Melrose Avenue. 21.^ 
Mendocino Mountains. 230 
Plateau. 164. 230 
Range. 1IV4 
Merced Canyon. 40 
River, 32 

canyon, 30 
Valley. 101 
Mesa Valley. 210 
Mesozoic. 10. 139. 141 

Mexican border. 99. 104. 107, 185, 197, 206, 210 
Mexico. 96. !I9. 103 
Middle Creek. 177 
dome. 1.52 
Farallon. 229 
Fork. 14. 1.5. 30. 52 

Canyon, 00 
Kern River. 57 
Ijike. 63. Sii. 85 
Mid-Pleistocene, 157, 160, 104, 170, 204, 210 
Mill Creek Canyon, 86 
Millerton Lake. 55 
Miller Mountain. 119 

Road. 119 
Mill Valley. 131 
.Mineral. 130 

King. 45 
Miocene, 10, 18, 23, 113, 205 
epoch, 157 
late. 25 
-Pliocene. 21 
strata, 93 

time, 19. 23. 50. 141. 157. 181 
valley, 25 
Miramontes, 166 
Mirror I^ke, 32, 55 
Mission Bay, '206, 211 

Beach, 211 
Modoc, 111 

County, 80, 82 
Indians, 113, 145 
Modoc Lava Beds, 82 

Plateau, 1.35. 139 
Plateau. 9, 111, 113, 11.5. 129 
section. O^i 
Mojave Desert, 9. 27, 63, 71, 89, 91, 99, 107, 189, 200 

River, 89, 91, 189 
Mokelumne, 15, 55, 147 
Mono, 14 

Basin, 76 
Cones, 181 
( 'raters, 79. 80 
-Inyo craters, 70 
Lake. 13. 14. 18. 27. 29, 52, 55, 57, 63, 70, 78. 

79, SO 
Range, .57. .80 
Montara block. 16t>. 170 

fault. 106; Mountain. 164, 166 
Montezuma Hills, 146, 147 
Monterey Bay, 104, 170, 223 
Canyon. 223, 2-29 
Peninsula, 225 

Monument, 115 
.Monumental, 141 
.Morena valley, 200 
.Morgan Hill, 132 
Mormon Point, 73 
Mosquito Pass, 4.i 
Mossbrne Falls. 1'28 
Mount Baker. 122 131 

Buckingham, 177 

l>ana, 47 

Diablo, 176 

E.ldy, 145 

(iibbs, 47 

Ouyot, .50 

Hamilton. 176 

Range, 164 

Harkness, 132 

Helen, 132 

Hitchcock. 51 

Hoffman. 129 

King. 52 

Konocti. 177. 180 

Langley, 13. 47 

Le Conte, 51 

Lyell. 30 

Mallory, 51 

McAdie, 51 

McClure, 30 

Montgomery, 60 

Parker, 78 

Rainier, 122 

Ritter, 57 

Rose, 21 

Russell, 51 

San Antonio. 189 
Jacinto. 107 

Shasta. 9. 119. 120, 121, 122, 128, 129. 130, 

Tallac, 13, 21 

Tamalpais, 164 

Willinm.son, 13. 19 

Wbitney, 13, 19, 25, 43, 45, 47. 49, 50, 51, 52. 

Wood, 7S 

Young, 49 
Mud Creek, 122 

volcanoes, 107 
Muir, 4.5. 46. 47 
Crest. 51 

McCain Spring. 100 

Cains Plateau, 197. 200 
Cloud. 113. 127. I'JS 

Rivers. \XI. 145 
Coy Mountains, 107 
CJavin Peak. 119 
(lee Canyon, 18 
KitlrickHills, 150 

Napa, 104 
.Navarro River, 2.10 




Nrslor. 210 

Terrnc*. 211 71.S2. IM.IU 
lH>nlfr. IC. Hi 
K.ills. 3S. -m 
Ncwi.rk. 172 
NewjMtrt Ut'ju-b. 205 
Canyon. 22.'i 
-Inel*'w**<wl. Iil3 
SiKiiiil Hill. 21H 
Nfw Uivrr. im. ION 

York-rrovuIeiuT Mountains. SO 
Niles. 17t; 
Xwinilay Rock, 22» 
Ni>IMih llancfs, .SO 
Noriliii 14 
North AiniTi.-n. 13. 119.219 
Itutte. 14.S 
Chnlonp IVak. ISO 
Home, ir>2 
Karallon. 220 
Fork. 1.".. 29. 52. 179. 180 
Inland. 20C. 211 

Oak Creek. .".7 ° 

<*oe.Tn Boulevanl. 211 
Ojai. 1S."> 

Basin. ISO 
Valley. 1S6 
(till Dail Mountains. SO ISO 
Station. 130 
Town. 211 
Olicocene. 10 

epoch. 23 
( >lvni]>ic Mount.-iins. 14 

( ireson. 1.-.. Nl. s-.>. 111. 113. 119. 128, !.■», 219. 225 
lM.rder. i:ffl.l42 
Coast Uaoges, 130 
Otay. 2f« 

Mesa. 211 
Mountains. 197 
Owens Ijjke. 14. IS. 19. 29, 63. 64, 67. 75 
Kiver. 14. tS<. 75 

\\illev. 13. IS. 19, 27. 4C. .57. 63, 64. 05, 66. 
67. 6.S. CO. 75, 70. 107. 206. 211 

Pacific basin, IG 
Beach. 211 
Coast. IC. 

( icean. IS. 1.57. 170. 172. ISC. 193. 197 
Pactntna Creek. VM 
Padre Juan Cnnyon. 186 
Pa jar.. Kiver. Ili4. 170 
Palen Mountain. 107 
Paleozoic rm-ks. 139 
Palisade clacier, 30 
Palisades. .57 
Palm Canyon. 107 

Sprints. 99. 197. 203 
Sution, 107 
City, 211 

Palomar. 200.206 

Mountains. 213 
Palo Verde Mesa. ',M. lOS 

Mountain ninpes. 107 
Vallev. ".M. lOS 
Palos Verdes Hills, VM. 203. 204, 213. 220 
Panamint Mountain. (t4 

ranKe.eS.tH. 71.72, 75 
Valley. 27. 63. 04. 71, 75 
Panther Creek. 122 
Panuni Crater, .'^t 
Paoha Island. 76 
J*ardee Reservoir. 55 
Parker. IM 

Creek. 120 
Dam, 94 
Peak, 47 
Pasadena. ISo. ISO 
Peninsular Itanges. 10. 15, 197, 200, 206, 210, 213 

system, 197 
Petaluma, 164 

Creeks, 172 
Phillips. 43 
Pier|K>nt Bay. 1S7 
Pillar Point. ICt! 
Pilot Knob. 94, 00, ia3 
Valley, 75 
Pinnacles, 75 

National Monument, ISO, ISl 
Itanger Station. 181 
Pitas Point. 187 
Pit Biver. SO. 113. 1.30. 1,39, 145 

Valley. 82 del Bey. 21.3, 215 
Pleasant I^nke, ,52 

PleistiK^ne. 10. l.S. 57. 110. IGO, 229 
deformation, 157 
eiK>ch. 71.82, 205 
lakes. ISO 
lava. 177 
mountain. 170 
rocks. 103 
sen. 2t>5 

time. 22. ,S0. 119. 127. 141. 145. 185. 193, 
203. 204. 205. 211 
Pliocene, 10, 71. 72. 205 

•early Pleistocene, 19 
epoch, IS. S2. i:iO. 1.57. 193 
late. 25. 170. 204 
time. IH. 110. 12<l. 141 
Pluto's Cave. 120 
Point Ai'io Nuevo. 223. 224 
Arena. 225 

Conception. 194, 223, 225, 229 
Dunie, 193 
Kerniin, 2<V4 
i:orda, 225 206, 210. 211 
Kcyes. 170. 229 

Peninsula. 166 
Sur. 223 

Portut:uese Point, 204 
I'otreru, 213 

.San Pnhlo, 172 
Poverty Hills, M 
Powny Terrat.e. 210 
Pnisppct IVak. 131 
Puenle Hills. 2t)3 
Puerto Kalso. 211 
Pumice Hutte, ,57 

Klat. 45. ,57 
Pyramid I^ke, 14.03 
Peak. 43 

Kange, 43 

Quail Mountain, 128 


liacoon Pass, 172 

Strait, 170 
Uainbow Fall. 57 

Raker Peak. 131. 132 
Randsburt. 75. S!t 
Re<l Banks. 122. 177 

Bluff, 130. 14.5. 1.56 

Butte. 12s 
Beddine. 111.113. 142. 145 
-Alturas road. 130 
Bedl.inds. 1S5 
lte.l Mountain. 09. i:{2, 1.39, 185, 186 

Uock Island. 170 
Redwood Peak. 17i; 
Reds Meadow. 57 
Reno. 14 
Reversed Creek. 7S, 70 

Creek-Rush Creek canyon, 78 
Valley, 76 
Rhett Lake. 113 
Ribbon Falls, 40 
Richardson Bay, 166 
Richmond, 176 Hills, 172 
Bincon Mountain. 1S5. 186, 187 
Ritter Range. 44. 45 
Rising River. 136 
Riverside. 94. 185. 197 
Rockbound Basin. 4^1 
Valley. 43 
BiK-k Canyon. 51 
Rockies. It; 

Bocky Mountains. 13. 14. 110 
Rogue River. 141 
Rosecrans. 213 
Rose Valley. M 

Russian River. 164. 170. 176. 230 
Round Tap. 170 

Valley. 19 
Royal Arches. 40 
Rubicon Peak. 21 
Hush. 7S 

Creek, 76, 78, 79 
Russell, 46 
Russia, 10 


Russian P«ik, ISO 

Uiver, 1114.170,172. 171".. 230 
Uustic Canyon, 103 

Sacramento. 14. 14.".. 147. l.-.(). 1.-.2, 17C 
liasin. 147 
Caiivnn. 12S 
Uiver. 127. 12S, 130. 141. 142. 14.j. 140, 

ltV4. ItUi, 170, 172. 170, 177 
Valle.v. .-..">. 1.30. 142, 14.'>, 146, 147, 148 
Saline Valley. U'.l. 210 
Salmon. 141 

Mountain. 141 
Salton Rasin, 103. 104, 107, lOS 

Sea, 00. 1(K», 103. KM, 107. lOS 
Salt WelKs (*anyon. 7.% 

Vallev, 7.'> 
San Andreas. 5.'). .SO. 107. 100. 164. 180, 225 
fault.170.lSl, 203, 225 
rift. 100. 170.176 
Sprinss, 164 
system. 176 
zone, ISO 
Antonio Canyon, ISO 

Creek. 180 
Bernardino, 185. 200. 205. 220 
Conntv. 74 
Mountains. 71. SO, 00, 189, 200, 

Uange, 185, 203, 220 
Borja, 107 

I4runo fault, 104. 170 
Hills, IW 
Mountain, 164 
Clemente, 104 

Island, 220 
Sand Hills, 04, 00, 100 
San Dieijo. 04. lS.->. 200. 210 
Bay. 211 

Mesa, 206, 210, 211 
region, 206 
Kiver. 206, 210,211 
Dimas cove, 204 
Felipe, 107 

Creek. 107 
Valley. KKI 
Fernando. 1S5. 204 

Valley, 103 
Francisco, l.">7, 160, 164, 170, 176 
Francisco area. 224 

bay, 14. 27. 5.5, 76. 145. 157, Iftl, 166, 

170. 172. 220, 230 
■Marin block. 170, 176 
Peninsula, 106 
Gabriel, 180. 205 

Canyon, 189 

Mountains, 80, 185, 189, 204. 205 
Uange, 180, 203, 2.H0 
River. 204 
Vallev. 204 


San Gorgonio Pass, 99, 100, 107. 20.3 
Peak. 189 
Jacinto. 90. KJO. 107. 107. 200 
fault, 205 

Mountain, 197, 203, 220 
ranges, 203 
Santa Rosa mass, 107 
Joaquin, 145. 140. 147, 152 
drainage. .51 
Mountain, 7-8 

Uiver, 14. 15. 20. 30. 45, 52, 53, .57, 1.50 
Valley. 14, 22, 55. 1,50, 152 
Jose-Mount Hamilton, 2.30 
Juan Seamount, 220, 224 
Mateo Point, 172 
Miguel, 185, ISO, 104, 107 
Nicolas. 104 

Island. 220 
Pedro. 16(1. 204 

Hill. 204. 205, 206 
Martir. 107 
Quentin Point. 1(M> 
Rafael Mountains. 157 
Ramon. 176. 104 

Valley, 176 

Santa Ana. 205 

Creek, 18,5, 186 
Mountains, 197, 203, 220 
Uiver, 189, 203, 205 
Valley, 185, 205 
Barbara, l.SO, 194 

County, 157 
Island, 193, 104 
Catalina, 220 
Clara Uiver, 18.5, 187 

Valley, 104, 170, 185, 186, 187 
("ruz. ISO 

Basin. 210, 220 
Island, 220 
Mountains, 164 
Fe Springs, 205, 206 

■Coyote uplift, 206 
Inez, 185, 200 

•Mountains, 185, 186 
Monicii, 103, 205 

anticline, 103 

Mountains, 185, 189, 193, 194, 205, 

Plain, 193 
Range, 103. 230 
region, 229 
Paula, 185 

Creek, 18.5, 186 
Rosa, 185, 180. 197 

Mountains, 99, 107, 197, 200 
Susana Mountains, 193 
Ynez Uange, 185 
Santiago Peak, 203 
Sawmill Creek. 6S, 09 
Mountains, 89 

Scott, 139 

Creek, 177 
Market, 141 
Scripps Institute. 210 
Seacliff station. 187 
Seal Beach. 213 
UtK-ks. 160 
Searles I.dike. 75 

Valley. 7I> 
Valley. 89 
Secret Spring Mountain. 119 
Sedimentary rocks, 17 
Sennor Canyon. 185 
Sentinel Home. 31 
Rock. 3S 
Sepulvetla Cany(Ui. 193 
Sequoia Natioual Forest. 52 

Park, 45 
Serra Cross. 187 
Seventeen Palms. 00 
Shasta, 121, 122, 127, 128 
County. 111. 141 
Dam. 55. 139, 142 
glaciers, 120 
Uiver, 120 

Valley. 119. 120, 121, 128 
Shastan activity, 127 
Sbastina, 121. 122, 128 
Sheep Hole Mountains, 89 
Sheller Cove, 224, 225 
Shepherd 45 
Shore Line Butte, 73 
Siberia, 27 
Sierra, 52. 150 

Buttes, 52 
■Cascade, 18 
Madre, 189 

Nevada. 9. 10, 13. 14. 1.5, 16. 17. 18. 10. 21, 
22, 23, 24, 25, 27, 29, 30. 43. 44. 45. 47. 50. 
51. 52. 54. 63. 64, 65, 07, tl8. 69. 71. 75. 76. 
78. 79. 89. 110. 128, 130, 141. 142, 145, 
1.50. 1.57, 181, 107, 200, 219 
Sierran bedrock. 78 

canyons. 32, 55 
crest, 25 
fronts, 65 
geology, 13 
lakes, 55 
landscape, 23 
region, 19, 46, 51 
scarp, 19 
slope, 18 
Sierra Pelonn, 89 

San Juan de Dios, 197 
Valley, 21 
SignalHill, 205, 213,215 
Silurian Ijake, 80 
SilverLake,.52. 78, 79,80 

Strand. 2(X( 
Simi Hills. 103 

Siskiyou. 139 

County. 111.113 



Sixty-I^ike basin, 52 
SInip Kjilice. 7-1,75,89 
S.Hla Ijikc, S!> 

Basin, 1)1 
Soledail Mouutain, L>06, 211 
Suiioiiia, lt>4 

RniiRe, 164 
lUuk. 2.'J0 
Soulf Butte. I'.'O 

Han.h. 120. 121 
South Hulte, 14.") 

Chnlnue. 181 

dome. 152 
Southeru Oaliforuia, 1S5. 2ftl, 229 
I'liiitii- Uailroa<l, 14,104 
I'l-ak, 177 
South Farallou, 220 

Fork. IS), :«, 43, 57, 13!), 141 

Island. 211 

Pacilic Beach, 210 

Yolla Boll}-. i:ti) 
Spanish, 211 

discoveries, 103 
Spurr, .1. K.,63 
Stanislaus Kiver. 15, ,52, 152 
Stockton. 152 
Stony Creek. 146. 147, 133 
Stovepipe AVells, 7.3 
Strawberry Creek. 176 
Sntiway Cave, 136 
Sucarloaf Mountain, 136 
Snisun Kay. 146. 147. 1.50. 172, 176 
Sulphur Bank, 17!), 180 

Mountain, 185, 1S6 

Upland, 185 
Sunol. 176 
Superstition.!)!), 103 
Surprise Valley. SO, 82, 83, 85, 86. Ill 
Susie Lake, 43 
Sutter Buttes, 145, 148 

County, 147 
Sweetwater, 211 

Table Mountain, 47 
Taboose Creek, 68 
Tahoe. 78, 79 

basin, 21, 200 

fault basin, 43 
Tallac-Pick's Peak range, 41 
Tamalpnis. 166 
Tamarack. 14 
Tanner Banks. 220 
Tecolote Canyon, 210 
Tehama, 14i; 

County. 139 

Tehuchapi Ranee, 145 
Pass, 13. 2i) 
Mountains, 89, 150 
Telesco]>e Peak, 75 
Tetnescal, 193 

Wash, 201 
Tenaya Canyon. ;«), ;tJ, 38, 55 
Tennessee Cove, 106 
Terrace, 2tMJ 
Tertiary, 10,63 

deposits, 74 
material, 225 
rocks, 72, 193 
sediments, 142 
The Gardens, 82 

Incomparable A'alley. 19 
Minarets, 57 
Thompson Peak. l."!9 
Thousand Island Lake, .52 
Three Brothers, 31 
Thurston Lake, 177, 180 
Tia .Juana.210, 211 
'J'ibur4>n Peninsula, 166 
Timber Mountain. Ill 
Tionn, 78 

Pas-s, 29, 63. 70 
road, 78 
Tokopah Valley, ;i0 
Toawa UanKe. 57 
Valley, 57 
Tomales Bay, l(i(i, 170 
Tiipnuga Beach, 193 
Transverse Uanjie. 157, 18.5, 189, 194, 197, 200 

Ranges, 9, 10, 15, 16, 99 
Treasure Island. 170 
Triassic, 10 

strata, 139 
volcanics, 64 
Trinity Alps. 1,39 

County. 139 
Mountain. 141 
River. 141 
Trolleyway, 213 
Trout Creek, 57 
Truckee. 21 

Meadows, 19 

River, 14. 19. 21,43,63 

Canyon, 43 
Valley, 43 
Tueeulala Falls. 40 
Tuff. 204 

Tujunca Canyon, 189 
Tulare. 1,52 

Lake, 1.50 
Tule Lake. 111. 113 
basin. 111 

Tunjtsten Hills. 04 
Tunio'l, 57 

Tuolunuie Canyon, 2!) 
Meadows, .5.5 
River, 1.5 
Twin Lakes, .55 
TynibiH. 46 

Creek,. 50 

TTbehebe.Croters, 73 
Union Pacific Railroad, .89 
United States, 13, 14, 27. 72. 99, 100, 219, 224 
Coast and Geodetic Survey, 213 

Guard, 229 
(Jeologieal Survey, 13, 63, 213 

Weather Bureau, 1.3 
Upper Lake, 8.3, 85 

Merced (.'anyon, 32 
Uppermost IMeistocene. 185 


Vallecito, 107 

\alley. 107 
Valle San Jose, 200 
Venice, 213, 215 
Ventura, 186 

County Courthouse, 187 

district. 185 

River. 185, 186, 187 

YaWey. 186. 187 
Vernal Falls. 38 
Vicente Mountains, 193 
Viejas, 200 
Vina, 146 
Volcan. 200 

Mountain. 213 
Volcano Creek, 57 
Vulcan's Castle, 132 

Walker River, 55 
Walnut Creek, 164 
Wallace Canyon, 51 

Creek, 50 
Warner block, 82 

Canvon, 82 

Mountains, 63, SO, 81, 82, 85, 86, 111, 145 

Range, SO, 82, S3, 85, 86 

\aUev, 80, 107, 130 
Washington, 14, 15, 82, 111, 119, 122 

Column, 32, 38 
Weaverville, 142 
Weitchpec, 1.39 
Westnaard Pass, 69 
Westmorland. UK\ 
West Peak, 164 
Whaleback, 119, 120 



Wbitf-lnj-o Mountains, 71 

Rungr, (Kt.tU. 66. 60 
Mountain. i:n.l3-.2 
I'dik, 61) 
Mountains front. 6.^ 
Whitney, 4li, 47. 127 
C'anvon. SI 
Creel!. 51. 128 
cliu'ier. 1-1 
Hill, 47, 50 

Puss, .')1 

reuion. 51 
Whittier. 2()4. 2I)."> 
Wildrose Canyon. 71 
Williams. ]4(i. 147 

-Clear Lake. 180 

Williamson. 46 
Willow Creek. 142 

Mountain, WJ 
Willows. 146 
Wilson (irove. 2:iO 
Wilson's Cove. in4 
Winyato I'ass, 74, 75 
Wiiitel-s, 147 
Wintun f;la<-i('r, 12S 

Yule University, 27 
Yellow Rutte. 120 
Yerha Huena Ishniil. 170 
Ytnacio \'alley, 17(> 
Yolo Basin. 14(1. 147. 177 

YoUn Holly Mountains. 141 
Yorkville, 230 
Yosemite Canyon. 32 

Falls, 40 

Klnciers. 29. 30 

landscape. 40 

National Park. 13, 2!>, 47, 76 

region, liO. 51 

-Tahoe repion. .30 

Valley. 2."i. 31. 32, 3S. 40. 52, 55 
Young summit. 47 
Yreka. 141 
Yulia Canyon. '27i 

Hiver. 1.-). .>S, 146, 147 
Yuma. Arizona, »!, 99, 103, 107 

tttfj in CALIPOBNIi 


60455 4-52 lOM 




C i 





Central alluvial plain, about 50 miles wide by 400 miles long, Ivlng between Coast 
Ranges and Sierra Nevada and containing a basin of inteiior d'ai lage at Its souttiem 
end Drained by Sacramento and San Joaouin Rivers, which |0in and enter San 
Francisco Bay, Eastern border (ormed by west-sloping Sierran bedroci* surface, 
which continues westward beneath alluvium and older sediments. Western border 
underlain by east-dipping Cretaceous and Cenozoic strata which form a deeply 
buried synclinal trough, lying beneath Great Valley along its western side. To the 
south, great oil fields follow anticlinal uplifts which mark the southwestern border 
of San Joaquin Valley and its southern basin. To the north, Sacramento Valley 
plain interrupted by Marysville Buttes, remnants of an isolated ancient volcano, 


A singular tilted tault-block ot great magnitude, nearly 400 miles long, presenting 
high, fugged multiple scarp face on eastern front, in contrast to gentle western 
slope (about 2'-) which disappears under sediments of Great Valley. Deep 
nver-cut canyons down western slope, their upper courses, especially in mas- 
sive granites ot higher Sierra, modified by gtactal sculpturing, forming such 
scenic features as Yosemite Valley. High continuous crest-line culminating in Mt. 
Whitney (elevation, 14.495.81 1 feet above sea level, highest point m United States) 
near eastern scarp. Glacial moraines and alluvial tans spreading over fault ntts 
and dropped blocks along eastern base of range. Metamorphic bedrock (still 
partly capped by Tertiary volcamcs), containing gold-bearing veins, with north-south 
structural trend, predominant in western flank and northern end ot Sierra. Northern 
Sierra boundary definitely marked where bedrock disappears under Cenozoic 
volcanic cover of Cascade Range, Southern Sierra terminated by Garlock fault, 
whicti forms northern border of Mojave Desert, and by San Andreas fault on the 
west where Sierra loins Southern Coast Ranges. 

Cham of volcanic cones, southern entension ot province which passes through 
Oregon and Washington. Dominatad by Mt- Shasta, glacier-mantled volcanic 
cone, elevation 14,152 feet above sea level. Terminated on the south by Lassen 
Peak, the only active volcano in the United States. Transected by deep canyons of 
Pit River which flows through range between these two major volcanic cones, after 
winding across interior Modoc Plateau on way to Sacramento River. 


Interior platform (elevation 4000-6000 feet above sea level), southern extension 
of Oregon lava plateau, consisting of thick accumulation ot lava tlows and tutf beds 
with many small volcanic cones. Occasional lakes, marshes, and sluggishly flowing 
streams- North -south faults m evidence. Province bounded indefinitely by 
Cascade Range on west and by Basin-Ranges on east and south. 


Accompanying Geologic Map 





Complex rugged topography. Prominent peaks and ridges 6000-8000 feet above 
sea level- Drainage transverse and irregular, developed on uplifted plateau. 
Entire mountain mass cut througn by Klamath River Successive benches with 
gold-bearmg gravels on sides ot canyons. Province more closely allied to Sierra 
Nevada than to Coast Ranges, with hard pre-Cretaceous rocks ejiposed by dis- 
section. Province continues into Oregon. VolcaniQ rocks of Cascade Range on 
east boundary; Cretaceous sediments on southelast; Franciscan and younger 
Coast Range formations, traversed by longitudinal faults, on southwest. 


System of longitudinal mountain-ranges (2000 to 4000, occasionally 6000 feet 
elevation above sea level) and valleys. Trend, N. 30" to 40° W,, controlled by 
folding and faulting. Province terminated on east where strata dip beneath 
alluvium of Great Valley; on west by Pacific Ocean with mountains rising sharply 
from uplifted and terraced, wave-cut coast; on north by South Fork Mountains, 
which possess characteristic trend ot Coast f?anges, but geology of Klamath Moun- 
tains ; on south, by Transverse Ranges, differing distinctly in structural trend, but 
containing thick series of late MesoJOic and Cenozoic sedimentary strata in 
common with Southern Coast Ranges. Continuity of coastal mountain-trend cut 
off obliquely by open embayments and by change in general direction of coast line, 
especially to the north. Northern and southern ranges separated by depression 
of San Francisco Bay area. Continental shelf transected by many submarine can- 
yons (Mendocino submarine scarp, probably produced by faulting; Monterey 
submarine canyon, 10,000 feet deep, apparently a submerged river canyon). 
Northern Coast Ranges dominated by irregular, knobby, landslide-topography of 
Franciscan formation. Contains fault valleys as yet unmapped. Eastern border 
characleri2ed by strike-ridges and valleys m Upper Mesozoic strata. Volcanic cones 
and flows south of Clear Lake. San Francisco Bay area and southern Coast 
Ranges more diversified and complex, largely controlled by structure of Cenozoic, 
Cretaceous, and Franciscan sediments. Dominated by ritt of active San Andreas 
fau't, trend slightly oblique to adjacent ranges, total length over 600 miles from 
Pt. Arena to Gulf of California idisplacement during 1906 earthquake horizontal, 
with coast side moving northward]. Coast Range granitic core, extending from 
southern extremity of Coast Ranges to Farallon Islands, bounded by San Andreas 
fault on east and by Nacimiento fault zone on west. 


Complex series of mountain ranges and valleys distinguished by dominant east-west 
trend m contrast to NW-SE direction o! Coast Ranges and Peninsular Ranges which 
the Transverse Ranges separate. Structural trends (NW-SE and NE-SW) sub- 
ordinate to maior east-west direction, significant m the formation of important oil 
field structures. Cenozoic sedimentary section one of the thickest in the world. 
Western limit ol province, island group t San Miguel, Santa Rosa, and Santa Cruz 
Islands); eastern limit, within Mojave Desert, including San Bernardino Mts., 
ilying on east side of San Andreas fault (trend of fault. N.60°W., a change of 20° 
'in direction from its alignment in the Coast Ranges). 


*A series of ranges separatea by longitudinal vaiieys, trending NW-SE. conditioned 
by erosion along faults, representing active branches of San Andreas system 
Trend of topography like that of Coast Ranges, but geology more like that of Sierra 
Nevada, dominating rocks bemg granitic, intruded into older metamorphic series. 
Province continuous into Lower California, Bounded on east by Colorado Desert 
in series of right-angle ]ogs due to interruption of fault traces. Los Angeles Basin, 
and the island group (Santa Catalina, Santa Barbara, and the distinctly terraced 
^an Clemente and San Nicolas Islands), together with surrounding continental 
shelf (cut by deep submarine fault troughs) included in this province. 


A low-lying barren desert basin, in part (about 245 feet) below sea level, dominated 
by Salton Sea. Province a depressed block between active branches of alluvium- 
covered San Andreas fault with southern extension of Mojave Desert on east. 
Characterized by ancient beach lines and silt deposits of extinct Lake Cahuilla. 


Broad interior region of isolated mountain ranges separated by expanses of desert 
plains. Inclosed drainage with playas, except for Colorado River bordering province 
on east. Two important fault trends: NW-SE, more prominent; east-west. 
secondary (apparent alignment with Transverse Ranges significant). Province 
wedged in sharp angle between Garlock fault (southern boundary Sierra Nevada) 
and San Andreas fault, where it bends east from major trend. Separated from 
prominent Basin-Ranges by eastern extension of Garlock fault. 


Distinctly a Nevada province lying wholly within the Great Basin. Interior drainage 
with lakes and playas. Typical fault-block structure, made up of roughly parallel 
ranges alternating with basins or troughs. Death Valley, lowest area m United 
States I 280 leet below sea leveM. one of these troughs or graben Another, Owens 
Valley, lying between bold eastern fault-scarp of Sierra Nevada and Inyo Mountains. 
To the north.Modoc Plateau lying between Basin-Ranges and Cascade Range. 







Surface contour interval 2000 feet (lOOOfoot contour stiown 
witfi dasties). 

Submarine contour interval 250 fatficms (100-fathom line 
indicating limit of continental sfielf, sfiown witti dasfies). 

Acknowledgments. Submarine contours by F. P. Sfiepard 
(Geol Soc Am) after data of U, S C, & G. S. and U. S G S 
Faults after new state geologic map Definition of geomorptiic 
provinces compiled from many sources, publistied and un- 





Lil.iv. W^ Y 
























' r 


'\ V 


, -^ ' If / 



Prepared by a ipecial technique o( shading a toposraphic nup, scale 11, 000 ,000. m 
color, and reducing il pholographicaliy lo (he scale 1 2,000,000 Plate names, county bounda- 
ries, elevations, contours fault lines, and physiographic data appwi on the accompanying 
Geomorphic Mop of Co/ifoinio, scale 1:2,000,000, originally published on Sheet III of the 
Gec/og.t Mop ol Calilnmio. 1 938, by Olaf P. Jenkins. 




160 MILES 




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1 C 





FEB 3 


FEB - 7 2000 
MAft - 6 2000!;: 


MAR I 2 Z000| 
Physical Sciences! 

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JM 88 -BS 

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Automated Phons Renewal ,24.hou0-. (530,762-1132 

D4613 (4«9)M 




California. Division 
of Mines. 

[1 ::.^^s) 

Call Number: 


no. 158 






of Mines. 



no. 158 

SCIENCES (2 maps) -rriOo^, io-ai-2-. 



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